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Overview
Comment:Split out the bulk of the actual VDBE code generation logic from where.c into a new file, leaving behind the analysis logic. This makes the original where.c smaller and hopefully easier to edit.
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Timelines: family | ancestors | descendants | both | view-optimization
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SHA1: faa0e420e93a2bc1c84df9eb9fef4748d29ce339
User & Date: drh 2015-06-06 20:12:09.183
Context
2015-06-08
14:23
Split more subfunctions of where.c out into a new whereexpr.c source file, for improved maintainability. (check-in: 46ef95c108 user: drh tags: view-optimization)
2015-06-06
20:12
Split out the bulk of the actual VDBE code generation logic from where.c into a new file, leaving behind the analysis logic. This makes the original where.c smaller and hopefully easier to edit. (check-in: faa0e420e9 user: drh tags: view-optimization)
18:30
Code simplifications in select.c and where.c. (check-in: 4f20ac90bc user: drh tags: view-optimization)
Changes
Unified Diff Ignore Whitespace Patch
Changes to Makefile.in.
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         mutex.lo mutex_noop.lo mutex_unix.lo mutex_w32.lo \
         notify.lo opcodes.lo os.lo os_unix.lo os_win.lo \
         pager.lo parse.lo pcache.lo pcache1.lo pragma.lo prepare.lo printf.lo \
         random.lo resolve.lo rowset.lo rtree.lo select.lo status.lo \
         table.lo threads.lo tokenize.lo trigger.lo \
         update.lo util.lo vacuum.lo \
         vdbe.lo vdbeapi.lo vdbeaux.lo vdbeblob.lo vdbemem.lo vdbesort.lo \
         vdbetrace.lo wal.lo walker.lo where.lo utf.lo vtab.lo

# Object files for the amalgamation.
#
LIBOBJS1 = sqlite3.lo

# Determine the real value of LIBOBJ based on the 'configure' script
#







|







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         mutex.lo mutex_noop.lo mutex_unix.lo mutex_w32.lo \
         notify.lo opcodes.lo os.lo os_unix.lo os_win.lo \
         pager.lo parse.lo pcache.lo pcache1.lo pragma.lo prepare.lo printf.lo \
         random.lo resolve.lo rowset.lo rtree.lo select.lo status.lo \
         table.lo threads.lo tokenize.lo trigger.lo \
         update.lo util.lo vacuum.lo \
         vdbe.lo vdbeapi.lo vdbeaux.lo vdbeblob.lo vdbemem.lo vdbesort.lo \
         vdbetrace.lo wal.lo walker.lo where.lo wherecode.lo utf.lo vtab.lo

# Object files for the amalgamation.
#
LIBOBJS1 = sqlite3.lo

# Determine the real value of LIBOBJ based on the 'configure' script
#
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  $(TOP)/src/vdbeInt.h \
  $(TOP)/src/vtab.c \
  $(TOP)/src/vxworks.h \
  $(TOP)/src/wal.c \
  $(TOP)/src/wal.h \
  $(TOP)/src/walker.c \
  $(TOP)/src/where.c \

  $(TOP)/src/whereInt.h

# Source code for extensions
#
SRC += \
  $(TOP)/ext/fts1/fts1.c \
  $(TOP)/ext/fts1/fts1.h \







>







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  $(TOP)/src/vdbeInt.h \
  $(TOP)/src/vtab.c \
  $(TOP)/src/vxworks.h \
  $(TOP)/src/wal.c \
  $(TOP)/src/wal.h \
  $(TOP)/src/walker.c \
  $(TOP)/src/where.c \
  $(TOP)/src/wherecode.c \
  $(TOP)/src/whereInt.h

# Source code for extensions
#
SRC += \
  $(TOP)/ext/fts1/fts1.c \
  $(TOP)/ext/fts1/fts1.h \
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  $(TOP)/src/util.c \
  $(TOP)/src/vdbeapi.c \
  $(TOP)/src/vdbeaux.c \
  $(TOP)/src/vdbe.c \
  $(TOP)/src/vdbemem.c \
  $(TOP)/src/vdbetrace.c \
  $(TOP)/src/where.c \

  parse.c \
  $(TOP)/ext/fts3/fts3.c \
  $(TOP)/ext/fts3/fts3_aux.c \
  $(TOP)/ext/fts3/fts3_expr.c \
  $(TOP)/ext/fts3/fts3_term.c \
  $(TOP)/ext/fts3/fts3_tokenizer.c \
  $(TOP)/ext/fts3/fts3_write.c \







>







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  $(TOP)/src/util.c \
  $(TOP)/src/vdbeapi.c \
  $(TOP)/src/vdbeaux.c \
  $(TOP)/src/vdbe.c \
  $(TOP)/src/vdbemem.c \
  $(TOP)/src/vdbetrace.c \
  $(TOP)/src/where.c \
  $(TOP)/src/wherecode.c \
  parse.c \
  $(TOP)/ext/fts3/fts3.c \
  $(TOP)/ext/fts3/fts3_aux.c \
  $(TOP)/ext/fts3/fts3_expr.c \
  $(TOP)/ext/fts3/fts3_term.c \
  $(TOP)/ext/fts3/fts3_tokenizer.c \
  $(TOP)/ext/fts3/fts3_write.c \
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walker.lo:	$(TOP)/src/walker.c $(HDR)
	$(LTCOMPILE) $(TEMP_STORE) -c $(TOP)/src/walker.c

where.lo:	$(TOP)/src/where.c $(HDR)
	$(LTCOMPILE) $(TEMP_STORE) -c $(TOP)/src/where.c




tclsqlite.lo:	$(TOP)/src/tclsqlite.c $(HDR)
	$(LTCOMPILE) -DUSE_TCL_STUBS=1 -c $(TOP)/src/tclsqlite.c

tclsqlite-shell.lo:	$(TOP)/src/tclsqlite.c $(HDR)
	$(LTCOMPILE) -DTCLSH=1 -o $@ -c $(TOP)/src/tclsqlite.c

tclsqlite-stubs.lo:	$(TOP)/src/tclsqlite.c $(HDR)







>
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walker.lo:	$(TOP)/src/walker.c $(HDR)
	$(LTCOMPILE) $(TEMP_STORE) -c $(TOP)/src/walker.c

where.lo:	$(TOP)/src/where.c $(HDR)
	$(LTCOMPILE) $(TEMP_STORE) -c $(TOP)/src/where.c

wherecode.lo:	$(TOP)/src/wherecode.c $(HDR)
	$(LTCOMPILE) $(TEMP_STORE) -c $(TOP)/src/wherecode.c

tclsqlite.lo:	$(TOP)/src/tclsqlite.c $(HDR)
	$(LTCOMPILE) -DUSE_TCL_STUBS=1 -c $(TOP)/src/tclsqlite.c

tclsqlite-shell.lo:	$(TOP)/src/tclsqlite.c $(HDR)
	$(LTCOMPILE) -DTCLSH=1 -o $@ -c $(TOP)/src/tclsqlite.c

tclsqlite-stubs.lo:	$(TOP)/src/tclsqlite.c $(HDR)
Changes to Makefile.msc.
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         mutex.lo mutex_noop.lo mutex_unix.lo mutex_w32.lo \
         notify.lo opcodes.lo os.lo os_unix.lo os_win.lo \
         pager.lo pcache.lo pcache1.lo pragma.lo prepare.lo printf.lo \
         random.lo resolve.lo rowset.lo rtree.lo select.lo status.lo \
         table.lo threads.lo tokenize.lo trigger.lo \
         update.lo util.lo vacuum.lo \
         vdbeapi.lo vdbeaux.lo vdbeblob.lo vdbemem.lo vdbesort.lo \
         vdbetrace.lo wal.lo walker.lo where.lo utf.lo vtab.lo

# Object files for the amalgamation.
#
LIBOBJS1 = sqlite3.lo

# Determine the real value of LIBOBJ based on the 'configure' script
#







|







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         mutex.lo mutex_noop.lo mutex_unix.lo mutex_w32.lo \
         notify.lo opcodes.lo os.lo os_unix.lo os_win.lo \
         pager.lo pcache.lo pcache1.lo pragma.lo prepare.lo printf.lo \
         random.lo resolve.lo rowset.lo rtree.lo select.lo status.lo \
         table.lo threads.lo tokenize.lo trigger.lo \
         update.lo util.lo vacuum.lo \
         vdbeapi.lo vdbeaux.lo vdbeblob.lo vdbemem.lo vdbesort.lo \
         vdbetrace.lo wal.lo walker.lo where.lo wherecode.lo utf.lo vtab.lo

# Object files for the amalgamation.
#
LIBOBJS1 = sqlite3.lo

# Determine the real value of LIBOBJ based on the 'configure' script
#
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  $(TOP)\src\vdbeInt.h \
  $(TOP)\src\vtab.c \
  $(TOP)\src\vxworks.h \
  $(TOP)\src\wal.c \
  $(TOP)\src\wal.h \
  $(TOP)\src\walker.c \
  $(TOP)\src\where.c \

  $(TOP)\src\whereInt.h

# Source code for extensions
#
SRC3 = \
  $(TOP)\ext\fts1\fts1.c \
  $(TOP)\ext\fts1\fts1.h \







>







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  $(TOP)\src\vdbeInt.h \
  $(TOP)\src\vtab.c \
  $(TOP)\src\vxworks.h \
  $(TOP)\src\wal.c \
  $(TOP)\src\wal.h \
  $(TOP)\src\walker.c \
  $(TOP)\src\where.c \
  $(TOP)\src\wherecode.c \
  $(TOP)\src\whereInt.h

# Source code for extensions
#
SRC3 = \
  $(TOP)\ext\fts1\fts1.c \
  $(TOP)\ext\fts1\fts1.h \
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  $(TOP)\src\vdbeapi.c \
  $(TOP)\src\vdbeaux.c \
  $(TOP)\src\vdbe.c \
  $(TOP)\src\vdbemem.c \
  $(TOP)\src\vdbesort.c \
  $(TOP)\src\vdbetrace.c \
  $(TOP)\src\where.c \

  parse.c \
  $(TOP)\ext\fts3\fts3.c \
  $(TOP)\ext\fts3\fts3_aux.c \
  $(TOP)\ext\fts3\fts3_expr.c \
  $(TOP)\ext\fts3\fts3_tokenizer.c \
  $(TOP)\ext\fts3\fts3_tokenize_vtab.c \
  $(TOP)\ext\fts3\fts3_unicode.c \







>







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  $(TOP)\src\vdbeapi.c \
  $(TOP)\src\vdbeaux.c \
  $(TOP)\src\vdbe.c \
  $(TOP)\src\vdbemem.c \
  $(TOP)\src\vdbesort.c \
  $(TOP)\src\vdbetrace.c \
  $(TOP)\src\where.c \
  $(TOP)\src\wherecode.c \
  parse.c \
  $(TOP)\ext\fts3\fts3.c \
  $(TOP)\ext\fts3\fts3_aux.c \
  $(TOP)\ext\fts3\fts3_expr.c \
  $(TOP)\ext\fts3\fts3_tokenizer.c \
  $(TOP)\ext\fts3\fts3_tokenize_vtab.c \
  $(TOP)\ext\fts3\fts3_unicode.c \
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walker.lo:	$(TOP)\src\walker.c $(HDR)
	$(LTCOMPILE) $(CORE_COMPILE_OPTS) -c $(TOP)\src\walker.c

where.lo:	$(TOP)\src\where.c $(HDR)
	$(LTCOMPILE) $(CORE_COMPILE_OPTS) -c $(TOP)\src\where.c




tclsqlite.lo:	$(TOP)\src\tclsqlite.c $(HDR)
	$(LTCOMPILE) $(NO_WARN) -DUSE_TCL_STUBS=1 -DBUILD_sqlite -I$(TCLINCDIR) -c $(TOP)\src\tclsqlite.c

tclsqlite-shell.lo:	$(TOP)\src\tclsqlite.c $(HDR)
	$(LTCOMPILE) $(NO_WARN) -DTCLSH=1 -DBUILD_sqlite -I$(TCLINCDIR) -c $(TOP)\src\tclsqlite.c

tclsqlite3.exe:	tclsqlite-shell.lo $(SQLITE3C) $(LIBRESOBJS)







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walker.lo:	$(TOP)\src\walker.c $(HDR)
	$(LTCOMPILE) $(CORE_COMPILE_OPTS) -c $(TOP)\src\walker.c

where.lo:	$(TOP)\src\where.c $(HDR)
	$(LTCOMPILE) $(CORE_COMPILE_OPTS) -c $(TOP)\src\where.c

wherecode.lo:	$(TOP)\src\wherecode.c $(HDR)
	$(LTCOMPILE) $(CORE_COMPILE_OPTS) -c $(TOP)\src\wherecode.c

tclsqlite.lo:	$(TOP)\src\tclsqlite.c $(HDR)
	$(LTCOMPILE) $(NO_WARN) -DUSE_TCL_STUBS=1 -DBUILD_sqlite -I$(TCLINCDIR) -c $(TOP)\src\tclsqlite.c

tclsqlite-shell.lo:	$(TOP)\src\tclsqlite.c $(HDR)
	$(LTCOMPILE) $(NO_WARN) -DTCLSH=1 -DBUILD_sqlite -I$(TCLINCDIR) -c $(TOP)\src\tclsqlite.c

tclsqlite3.exe:	tclsqlite-shell.lo $(SQLITE3C) $(LIBRESOBJS)
Changes to main.mk.
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         mutex.o mutex_noop.o mutex_unix.o mutex_w32.o \
         notify.o opcodes.o os.o os_unix.o os_win.o \
         pager.o pcache.o pcache1.o pragma.o prepare.o printf.o \
         random.o resolve.o rowset.o rtree.o select.o sqlite3ota.o status.o \
         table.o threads.o tokenize.o trigger.o \
         update.o userauth.o util.o vacuum.o \
         vdbeapi.o vdbeaux.o vdbeblob.o vdbemem.o vdbesort.o \
	 vdbetrace.o wal.o walker.o where.o utf.o vtab.o



# All of the source code files.
#
SRC = \
  $(TOP)/src/alter.c \







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         mutex.o mutex_noop.o mutex_unix.o mutex_w32.o \
         notify.o opcodes.o os.o os_unix.o os_win.o \
         pager.o pcache.o pcache1.o pragma.o prepare.o printf.o \
         random.o resolve.o rowset.o rtree.o select.o sqlite3ota.o status.o \
         table.o threads.o tokenize.o trigger.o \
         update.o userauth.o util.o vacuum.o \
         vdbeapi.o vdbeaux.o vdbeblob.o vdbemem.o vdbesort.o \
	 vdbetrace.o wal.o walker.o where.o wherecode.o utf.o vtab.o



# All of the source code files.
#
SRC = \
  $(TOP)/src/alter.c \
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  $(TOP)/src/vdbeInt.h \
  $(TOP)/src/vtab.c \
  $(TOP)/src/vxworks.h \
  $(TOP)/src/wal.c \
  $(TOP)/src/wal.h \
  $(TOP)/src/walker.c \
  $(TOP)/src/where.c \

  $(TOP)/src/whereInt.h

# Source code for extensions
#
SRC += \
  $(TOP)/ext/fts1/fts1.c \
  $(TOP)/ext/fts1/fts1.h \







>







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  $(TOP)/src/vdbeInt.h \
  $(TOP)/src/vtab.c \
  $(TOP)/src/vxworks.h \
  $(TOP)/src/wal.c \
  $(TOP)/src/wal.h \
  $(TOP)/src/walker.c \
  $(TOP)/src/where.c \
  $(TOP)/src/wherecode.c \
  $(TOP)/src/whereInt.h

# Source code for extensions
#
SRC += \
  $(TOP)/ext/fts1/fts1.c \
  $(TOP)/ext/fts1/fts1.h \
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  $(TOP)/src/utf.c \
  $(TOP)/src/util.c \
  $(TOP)/src/vdbeapi.c \
  $(TOP)/src/vdbeaux.c \
  $(TOP)/src/vdbe.c \
  $(TOP)/src/vdbemem.c \
  $(TOP)/src/where.c \

  parse.c \
  $(TOP)/ext/fts3/fts3.c \
  $(TOP)/ext/fts3/fts3_aux.c \
  $(TOP)/ext/fts3/fts3_expr.c \
  $(TOP)/ext/fts3/fts3_tokenizer.c \
  $(TOP)/ext/fts3/fts3_write.c \
  $(TOP)/ext/async/sqlite3async.c 







>







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  $(TOP)/src/utf.c \
  $(TOP)/src/util.c \
  $(TOP)/src/vdbeapi.c \
  $(TOP)/src/vdbeaux.c \
  $(TOP)/src/vdbe.c \
  $(TOP)/src/vdbemem.c \
  $(TOP)/src/where.c \
  $(TOP)/src/wherecode.c \
  parse.c \
  $(TOP)/ext/fts3/fts3.c \
  $(TOP)/ext/fts3/fts3_aux.c \
  $(TOP)/ext/fts3/fts3_expr.c \
  $(TOP)/ext/fts3/fts3_tokenizer.c \
  $(TOP)/ext/fts3/fts3_write.c \
  $(TOP)/ext/async/sqlite3async.c 
Changes to src/where.c.
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** generating the code that loops through a table looking for applicable
** rows.  Indices are selected and used to speed the search when doing
** so is applicable.  Because this module is responsible for selecting
** indices, you might also think of this module as the "query optimizer".
*/
#include "sqliteInt.h"
#include "whereInt.h"










/*
** Return the estimated number of output rows from a WHERE clause
*/
u64 sqlite3WhereOutputRowCount(WhereInfo *pWInfo){
  return sqlite3LogEstToInt(pWInfo->nRowOut);
}







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** generating the code that loops through a table looking for applicable
** rows.  Indices are selected and used to speed the search when doing
** so is applicable.  Because this module is responsible for selecting
** indices, you might also think of this module as the "query optimizer".
*/
#include "sqliteInt.h"
#include "whereInt.h"

/* Forward declaration of methods */
static int whereLoopResize(sqlite3*, WhereLoop*, int);

/* Test variable that can be set to enable WHERE tracing */
#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
/***/ int sqlite3WhereTrace = 0;
#endif


/*
** Return the estimated number of output rows from a WHERE clause
*/
u64 sqlite3WhereOutputRowCount(WhereInfo *pWInfo){
  return sqlite3LogEstToInt(pWInfo->nRowOut);
}
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*/
#define initMaskSet(P)  (P)->n=0

/*
** Return the bitmask for the given cursor number.  Return 0 if
** iCursor is not in the set.
*/
static Bitmask getMask(WhereMaskSet *pMaskSet, int iCursor){
  int i;
  assert( pMaskSet->n<=(int)sizeof(Bitmask)*8 );
  for(i=0; i<pMaskSet->n; i++){
    if( pMaskSet->ix[i]==iCursor ){
      return MASKBIT(i);
    }
  }







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*/
#define initMaskSet(P)  (P)->n=0

/*
** Return the bitmask for the given cursor number.  Return 0 if
** iCursor is not in the set.
*/
Bitmask sqlite3WhereGetMask(WhereMaskSet *pMaskSet, int iCursor){
  int i;
  assert( pMaskSet->n<=(int)sizeof(Bitmask)*8 );
  for(i=0; i<pMaskSet->n; i++){
    if( pMaskSet->ix[i]==iCursor ){
      return MASKBIT(i);
    }
  }
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*/
static Bitmask exprListTableUsage(WhereMaskSet*, ExprList*);
static Bitmask exprSelectTableUsage(WhereMaskSet*, Select*);
static Bitmask exprTableUsage(WhereMaskSet *pMaskSet, Expr *p){
  Bitmask mask = 0;
  if( p==0 ) return 0;
  if( p->op==TK_COLUMN ){
    mask = getMask(pMaskSet, p->iTable);
    return mask;
  }
  mask = exprTableUsage(pMaskSet, p->pRight);
  mask |= exprTableUsage(pMaskSet, p->pLeft);
  if( ExprHasProperty(p, EP_xIsSelect) ){
    mask |= exprSelectTableUsage(pMaskSet, p->x.pSelect);
  }else{







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*/
static Bitmask exprListTableUsage(WhereMaskSet*, ExprList*);
static Bitmask exprSelectTableUsage(WhereMaskSet*, Select*);
static Bitmask exprTableUsage(WhereMaskSet *pMaskSet, Expr *p){
  Bitmask mask = 0;
  if( p==0 ) return 0;
  if( p->op==TK_COLUMN ){
    mask = sqlite3WhereGetMask(pMaskSet, p->iTable);
    return mask;
  }
  mask = exprTableUsage(pMaskSet, p->pRight);
  mask |= exprTableUsage(pMaskSet, p->pLeft);
  if( ExprHasProperty(p, EP_xIsSelect) ){
    mask |= exprSelectTableUsage(pMaskSet, p->x.pSelect);
  }else{
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** If there are multiple terms in the WHERE clause of the form "X <op> <expr>"
** then try for the one with no dependencies on <expr> - in other words where
** <expr> is a constant expression of some kind.  Only return entries of
** the form "X <op> Y" where Y is a column in another table if no terms of
** the form "X <op> <const-expr>" exist.   If no terms with a constant RHS
** exist, try to return a term that does not use WO_EQUIV.
*/
static WhereTerm *findTerm(
  WhereClause *pWC,     /* The WHERE clause to be searched */
  int iCur,             /* Cursor number of LHS */
  int iColumn,          /* Column number of LHS */
  Bitmask notReady,     /* RHS must not overlap with this mask */
  u32 op,               /* Mask of WO_xx values describing operator */
  Index *pIdx           /* Must be compatible with this index, if not NULL */
){







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** If there are multiple terms in the WHERE clause of the form "X <op> <expr>"
** then try for the one with no dependencies on <expr> - in other words where
** <expr> is a constant expression of some kind.  Only return entries of
** the form "X <op> Y" where Y is a column in another table if no terms of
** the form "X <op> <const-expr>" exist.   If no terms with a constant RHS
** exist, try to return a term that does not use WO_EQUIV.
*/
WhereTerm *sqlite3WhereFindTerm(
  WhereClause *pWC,     /* The WHERE clause to be searched */
  int iCur,             /* Cursor number of LHS */
  int iColumn,          /* Column number of LHS */
  Bitmask notReady,     /* RHS must not overlap with this mask */
  u32 op,               /* Mask of WO_xx values describing operator */
  Index *pIdx           /* Must be compatible with this index, if not NULL */
){
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        exprAnalyzeAll(pSrc, pAndWC);
        pAndWC->pOuter = pWC;
        testcase( db->mallocFailed );
        if( !db->mallocFailed ){
          for(j=0, pAndTerm=pAndWC->a; j<pAndWC->nTerm; j++, pAndTerm++){
            assert( pAndTerm->pExpr );
            if( allowedOp(pAndTerm->pExpr->op) ){
              b |= getMask(&pWInfo->sMaskSet, pAndTerm->leftCursor);
            }
          }
        }
        indexable &= b;
      }
    }else if( pOrTerm->wtFlags & TERM_COPIED ){
      /* Skip this term for now.  We revisit it when we process the
      ** corresponding TERM_VIRTUAL term */
    }else{
      Bitmask b;
      b = getMask(&pWInfo->sMaskSet, pOrTerm->leftCursor);
      if( pOrTerm->wtFlags & TERM_VIRTUAL ){
        WhereTerm *pOther = &pOrWc->a[pOrTerm->iParent];
        b |= getMask(&pWInfo->sMaskSet, pOther->leftCursor);
      }
      indexable &= b;
      if( (pOrTerm->eOperator & WO_EQ)==0 ){
        chngToIN = 0;
      }else{
        chngToIN &= b;
      }







|










|


|







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        exprAnalyzeAll(pSrc, pAndWC);
        pAndWC->pOuter = pWC;
        testcase( db->mallocFailed );
        if( !db->mallocFailed ){
          for(j=0, pAndTerm=pAndWC->a; j<pAndWC->nTerm; j++, pAndTerm++){
            assert( pAndTerm->pExpr );
            if( allowedOp(pAndTerm->pExpr->op) ){
              b |= sqlite3WhereGetMask(&pWInfo->sMaskSet, pAndTerm->leftCursor);
            }
          }
        }
        indexable &= b;
      }
    }else if( pOrTerm->wtFlags & TERM_COPIED ){
      /* Skip this term for now.  We revisit it when we process the
      ** corresponding TERM_VIRTUAL term */
    }else{
      Bitmask b;
      b = sqlite3WhereGetMask(&pWInfo->sMaskSet, pOrTerm->leftCursor);
      if( pOrTerm->wtFlags & TERM_VIRTUAL ){
        WhereTerm *pOther = &pOrWc->a[pOrTerm->iParent];
        b |= sqlite3WhereGetMask(&pWInfo->sMaskSet, pOther->leftCursor);
      }
      indexable &= b;
      if( (pOrTerm->eOperator & WO_EQ)==0 ){
        chngToIN = 0;
      }else{
        chngToIN &= b;
      }
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        pOrTerm->wtFlags &= ~TERM_OR_OK;
        if( pOrTerm->leftCursor==iCursor ){
          /* This is the 2-bit case and we are on the second iteration and
          ** current term is from the first iteration.  So skip this term. */
          assert( j==1 );
          continue;
        }
        if( (chngToIN & getMask(&pWInfo->sMaskSet, pOrTerm->leftCursor))==0 ){
          /* This term must be of the form t1.a==t2.b where t2 is in the
          ** chngToIN set but t1 is not.  This term will be either preceded
          ** or follwed by an inverted copy (t2.b==t1.a).  Skip this term 
          ** and use its inversion. */
          testcase( pOrTerm->wtFlags & TERM_COPIED );
          testcase( pOrTerm->wtFlags & TERM_VIRTUAL );
          assert( pOrTerm->wtFlags & (TERM_COPIED|TERM_VIRTUAL) );
          continue;
        }
        iColumn = pOrTerm->u.leftColumn;
        iCursor = pOrTerm->leftCursor;
        break;
      }
      if( i<0 ){
        /* No candidate table+column was found.  This can only occur
        ** on the second iteration */
        assert( j==1 );
        assert( IsPowerOfTwo(chngToIN) );
        assert( chngToIN==getMask(&pWInfo->sMaskSet, iCursor) );
        break;
      }
      testcase( j==1 );

      /* We have found a candidate table and column.  Check to see if that
      ** table and column is common to every term in the OR clause */
      okToChngToIN = 1;







|


















|







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        pOrTerm->wtFlags &= ~TERM_OR_OK;
        if( pOrTerm->leftCursor==iCursor ){
          /* This is the 2-bit case and we are on the second iteration and
          ** current term is from the first iteration.  So skip this term. */
          assert( j==1 );
          continue;
        }
        if( (chngToIN & sqlite3WhereGetMask(&pWInfo->sMaskSet, pOrTerm->leftCursor))==0 ){
          /* This term must be of the form t1.a==t2.b where t2 is in the
          ** chngToIN set but t1 is not.  This term will be either preceded
          ** or follwed by an inverted copy (t2.b==t1.a).  Skip this term 
          ** and use its inversion. */
          testcase( pOrTerm->wtFlags & TERM_COPIED );
          testcase( pOrTerm->wtFlags & TERM_VIRTUAL );
          assert( pOrTerm->wtFlags & (TERM_COPIED|TERM_VIRTUAL) );
          continue;
        }
        iColumn = pOrTerm->u.leftColumn;
        iCursor = pOrTerm->leftCursor;
        break;
      }
      if( i<0 ){
        /* No candidate table+column was found.  This can only occur
        ** on the second iteration */
        assert( j==1 );
        assert( IsPowerOfTwo(chngToIN) );
        assert( chngToIN==sqlite3WhereGetMask(&pWInfo->sMaskSet, iCursor) );
        break;
      }
      testcase( j==1 );

      /* We have found a candidate table and column.  Check to see if that
      ** table and column is common to every term in the OR clause */
      okToChngToIN = 1;
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  }else if( op==TK_ISNULL ){
    pTerm->prereqRight = 0;
  }else{
    pTerm->prereqRight = exprTableUsage(pMaskSet, pExpr->pRight);
  }
  prereqAll = exprTableUsage(pMaskSet, pExpr);
  if( ExprHasProperty(pExpr, EP_FromJoin) ){
    Bitmask x = getMask(pMaskSet, pExpr->iRightJoinTable);
    prereqAll |= x;
    extraRight = x-1;  /* ON clause terms may not be used with an index
                       ** on left table of a LEFT JOIN.  Ticket #3015 */
  }
  pTerm->prereqAll = prereqAll;
  pTerm->leftCursor = -1;
  pTerm->iParent = -1;







|







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  }else if( op==TK_ISNULL ){
    pTerm->prereqRight = 0;
  }else{
    pTerm->prereqRight = exprTableUsage(pMaskSet, pExpr->pRight);
  }
  prereqAll = exprTableUsage(pMaskSet, pExpr);
  if( ExprHasProperty(pExpr, EP_FromJoin) ){
    Bitmask x = sqlite3WhereGetMask(pMaskSet, pExpr->iRightJoinTable);
    prereqAll |= x;
    extraRight = x-1;  /* ON clause terms may not be used with an index
                       ** on left table of a LEFT JOIN.  Ticket #3015 */
  }
  pTerm->prereqAll = prereqAll;
  pTerm->leftCursor = -1;
  pTerm->iParent = -1;
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  **   3. All of those index columns for which the WHERE clause does not
  **      contain a "col=X" term are subject to a NOT NULL constraint.
  */
  for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
    if( !IsUniqueIndex(pIdx) ) continue;
    for(i=0; i<pIdx->nKeyCol; i++){
      i16 iCol = pIdx->aiColumn[i];
      if( 0==findTerm(pWC, iBase, iCol, ~(Bitmask)0, WO_EQ, pIdx) ){
        int iIdxCol = findIndexCol(pParse, pDistinct, iBase, pIdx, i);
        if( iIdxCol<0 || pTab->aCol[iCol].notNull==0 ){
          break;
        }
      }
    }
    if( i==pIdx->nKeyCol ){







|







1646
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1658
1659
1660
  **   3. All of those index columns for which the WHERE clause does not
  **      contain a "col=X" term are subject to a NOT NULL constraint.
  */
  for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
    if( !IsUniqueIndex(pIdx) ) continue;
    for(i=0; i<pIdx->nKeyCol; i++){
      i16 iCol = pIdx->aiColumn[i];
      if( 0==sqlite3WhereFindTerm(pWC, iBase, iCol, ~(Bitmask)0, WO_EQ, pIdx) ){
        int iIdxCol = findIndexCol(pParse, pDistinct, iBase, pIdx, i);
        if( iIdxCol<0 || pTab->aCol[iCol].notNull==0 ){
          break;
        }
      }
    }
    if( i==pIdx->nKeyCol ){
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    WHERETRACE(0x10,("IN row estimate: est=%d\n", nRowEst));
  }
  assert( pBuilder->nRecValid==nRecValid );
  return rc;
}
#endif /* SQLITE_ENABLE_STAT3_OR_STAT4 */

/*
** Disable a term in the WHERE clause.  Except, do not disable the term
** if it controls a LEFT OUTER JOIN and it did not originate in the ON
** or USING clause of that join.
**
** Consider the term t2.z='ok' in the following queries:
**
**   (1)  SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x WHERE t2.z='ok'
**   (2)  SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x AND t2.z='ok'
**   (3)  SELECT * FROM t1, t2 WHERE t1.a=t2.x AND t2.z='ok'
**
** The t2.z='ok' is disabled in the in (2) because it originates
** in the ON clause.  The term is disabled in (3) because it is not part
** of a LEFT OUTER JOIN.  In (1), the term is not disabled.
**
** Disabling a term causes that term to not be tested in the inner loop
** of the join.  Disabling is an optimization.  When terms are satisfied
** by indices, we disable them to prevent redundant tests in the inner
** loop.  We would get the correct results if nothing were ever disabled,
** but joins might run a little slower.  The trick is to disable as much
** as we can without disabling too much.  If we disabled in (1), we'd get
** the wrong answer.  See ticket #813.
**
** If all the children of a term are disabled, then that term is also
** automatically disabled.  In this way, terms get disabled if derived
** virtual terms are tested first.  For example:
**
**      x GLOB 'abc*' AND x>='abc' AND x<'acd'
**      \___________/     \______/     \_____/
**         parent          child1       child2
**
** Only the parent term was in the original WHERE clause.  The child1
** and child2 terms were added by the LIKE optimization.  If both of
** the virtual child terms are valid, then testing of the parent can be 
** skipped.
**
** Usually the parent term is marked as TERM_CODED.  But if the parent
** term was originally TERM_LIKE, then the parent gets TERM_LIKECOND instead.
** The TERM_LIKECOND marking indicates that the term should be coded inside
** a conditional such that is only evaluated on the second pass of a
** LIKE-optimization loop, when scanning BLOBs instead of strings.
*/
static void disableTerm(WhereLevel *pLevel, WhereTerm *pTerm){
  int nLoop = 0;
  while( pTerm
      && (pTerm->wtFlags & TERM_CODED)==0
      && (pLevel->iLeftJoin==0 || ExprHasProperty(pTerm->pExpr, EP_FromJoin))
      && (pLevel->notReady & pTerm->prereqAll)==0
  ){
    if( nLoop && (pTerm->wtFlags & TERM_LIKE)!=0 ){
      pTerm->wtFlags |= TERM_LIKECOND;
    }else{
      pTerm->wtFlags |= TERM_CODED;
    }
    if( pTerm->iParent<0 ) break;
    pTerm = &pTerm->pWC->a[pTerm->iParent];
    pTerm->nChild--;
    if( pTerm->nChild!=0 ) break;
    nLoop++;
  }
}

/*
** Code an OP_Affinity opcode to apply the column affinity string zAff
** to the n registers starting at base. 
**
** As an optimization, SQLITE_AFF_BLOB entries (which are no-ops) at the
** beginning and end of zAff are ignored.  If all entries in zAff are
** SQLITE_AFF_BLOB, then no code gets generated.
**
** This routine makes its own copy of zAff so that the caller is free
** to modify zAff after this routine returns.
*/
static void codeApplyAffinity(Parse *pParse, int base, int n, char *zAff){
  Vdbe *v = pParse->pVdbe;
  if( zAff==0 ){
    assert( pParse->db->mallocFailed );
    return;
  }
  assert( v!=0 );

  /* Adjust base and n to skip over SQLITE_AFF_BLOB entries at the beginning
  ** and end of the affinity string.
  */
  while( n>0 && zAff[0]==SQLITE_AFF_BLOB ){
    n--;
    base++;
    zAff++;
  }
  while( n>1 && zAff[n-1]==SQLITE_AFF_BLOB ){
    n--;
  }

  /* Code the OP_Affinity opcode if there is anything left to do. */
  if( n>0 ){
    sqlite3VdbeAddOp2(v, OP_Affinity, base, n);
    sqlite3VdbeChangeP4(v, -1, zAff, n);
    sqlite3ExprCacheAffinityChange(pParse, base, n);
  }
}


/*
** Generate code for a single equality term of the WHERE clause.  An equality
** term can be either X=expr or X IN (...).   pTerm is the term to be 
** coded.
**
** The current value for the constraint is left in register iReg.
**
** For a constraint of the form X=expr, the expression is evaluated and its
** result is left on the stack.  For constraints of the form X IN (...)
** this routine sets up a loop that will iterate over all values of X.
*/
static int codeEqualityTerm(
  Parse *pParse,      /* The parsing context */
  WhereTerm *pTerm,   /* The term of the WHERE clause to be coded */
  WhereLevel *pLevel, /* The level of the FROM clause we are working on */
  int iEq,            /* Index of the equality term within this level */
  int bRev,           /* True for reverse-order IN operations */
  int iTarget         /* Attempt to leave results in this register */
){
  Expr *pX = pTerm->pExpr;
  Vdbe *v = pParse->pVdbe;
  int iReg;                  /* Register holding results */

  assert( iTarget>0 );
  if( pX->op==TK_EQ || pX->op==TK_IS ){
    iReg = sqlite3ExprCodeTarget(pParse, pX->pRight, iTarget);
  }else if( pX->op==TK_ISNULL ){
    iReg = iTarget;
    sqlite3VdbeAddOp2(v, OP_Null, 0, iReg);
#ifndef SQLITE_OMIT_SUBQUERY
  }else{
    int eType;
    int iTab;
    struct InLoop *pIn;
    WhereLoop *pLoop = pLevel->pWLoop;

    if( (pLoop->wsFlags & WHERE_VIRTUALTABLE)==0
      && pLoop->u.btree.pIndex!=0
      && pLoop->u.btree.pIndex->aSortOrder[iEq]
    ){
      testcase( iEq==0 );
      testcase( bRev );
      bRev = !bRev;
    }
    assert( pX->op==TK_IN );
    iReg = iTarget;
    eType = sqlite3FindInIndex(pParse, pX, IN_INDEX_LOOP, 0);
    if( eType==IN_INDEX_INDEX_DESC ){
      testcase( bRev );
      bRev = !bRev;
    }
    iTab = pX->iTable;
    sqlite3VdbeAddOp2(v, bRev ? OP_Last : OP_Rewind, iTab, 0);
    VdbeCoverageIf(v, bRev);
    VdbeCoverageIf(v, !bRev);
    assert( (pLoop->wsFlags & WHERE_MULTI_OR)==0 );
    pLoop->wsFlags |= WHERE_IN_ABLE;
    if( pLevel->u.in.nIn==0 ){
      pLevel->addrNxt = sqlite3VdbeMakeLabel(v);
    }
    pLevel->u.in.nIn++;
    pLevel->u.in.aInLoop =
       sqlite3DbReallocOrFree(pParse->db, pLevel->u.in.aInLoop,
                              sizeof(pLevel->u.in.aInLoop[0])*pLevel->u.in.nIn);
    pIn = pLevel->u.in.aInLoop;
    if( pIn ){
      pIn += pLevel->u.in.nIn - 1;
      pIn->iCur = iTab;
      if( eType==IN_INDEX_ROWID ){
        pIn->addrInTop = sqlite3VdbeAddOp2(v, OP_Rowid, iTab, iReg);
      }else{
        pIn->addrInTop = sqlite3VdbeAddOp3(v, OP_Column, iTab, 0, iReg);
      }
      pIn->eEndLoopOp = bRev ? OP_PrevIfOpen : OP_NextIfOpen;
      sqlite3VdbeAddOp1(v, OP_IsNull, iReg); VdbeCoverage(v);
    }else{
      pLevel->u.in.nIn = 0;
    }
#endif
  }
  disableTerm(pLevel, pTerm);
  return iReg;
}

/*
** Generate code that will evaluate all == and IN constraints for an
** index scan.
**
** For example, consider table t1(a,b,c,d,e,f) with index i1(a,b,c).
** Suppose the WHERE clause is this:  a==5 AND b IN (1,2,3) AND c>5 AND c<10
** The index has as many as three equality constraints, but in this
** example, the third "c" value is an inequality.  So only two 
** constraints are coded.  This routine will generate code to evaluate
** a==5 and b IN (1,2,3).  The current values for a and b will be stored
** in consecutive registers and the index of the first register is returned.
**
** In the example above nEq==2.  But this subroutine works for any value
** of nEq including 0.  If nEq==0, this routine is nearly a no-op.
** The only thing it does is allocate the pLevel->iMem memory cell and
** compute the affinity string.
**
** The nExtraReg parameter is 0 or 1.  It is 0 if all WHERE clause constraints
** are == or IN and are covered by the nEq.  nExtraReg is 1 if there is
** an inequality constraint (such as the "c>=5 AND c<10" in the example) that
** occurs after the nEq quality constraints.
**
** This routine allocates a range of nEq+nExtraReg memory cells and returns
** the index of the first memory cell in that range. The code that
** calls this routine will use that memory range to store keys for
** start and termination conditions of the loop.
** key value of the loop.  If one or more IN operators appear, then
** this routine allocates an additional nEq memory cells for internal
** use.
**
** Before returning, *pzAff is set to point to a buffer containing a
** copy of the column affinity string of the index allocated using
** sqlite3DbMalloc(). Except, entries in the copy of the string associated
** with equality constraints that use BLOB or NONE affinity are set to
** SQLITE_AFF_BLOB. This is to deal with SQL such as the following:
**
**   CREATE TABLE t1(a TEXT PRIMARY KEY, b);
**   SELECT ... FROM t1 AS t2, t1 WHERE t1.a = t2.b;
**
** In the example above, the index on t1(a) has TEXT affinity. But since
** the right hand side of the equality constraint (t2.b) has BLOB/NONE affinity,
** no conversion should be attempted before using a t2.b value as part of
** a key to search the index. Hence the first byte in the returned affinity
** string in this example would be set to SQLITE_AFF_BLOB.
*/
static int codeAllEqualityTerms(
  Parse *pParse,        /* Parsing context */
  WhereLevel *pLevel,   /* Which nested loop of the FROM we are coding */
  int bRev,             /* Reverse the order of IN operators */
  int nExtraReg,        /* Number of extra registers to allocate */
  char **pzAff          /* OUT: Set to point to affinity string */
){
  u16 nEq;                      /* The number of == or IN constraints to code */
  u16 nSkip;                    /* Number of left-most columns to skip */
  Vdbe *v = pParse->pVdbe;      /* The vm under construction */
  Index *pIdx;                  /* The index being used for this loop */
  WhereTerm *pTerm;             /* A single constraint term */
  WhereLoop *pLoop;             /* The WhereLoop object */
  int j;                        /* Loop counter */
  int regBase;                  /* Base register */
  int nReg;                     /* Number of registers to allocate */
  char *zAff;                   /* Affinity string to return */

  /* This module is only called on query plans that use an index. */
  pLoop = pLevel->pWLoop;
  assert( (pLoop->wsFlags & WHERE_VIRTUALTABLE)==0 );
  nEq = pLoop->u.btree.nEq;
  nSkip = pLoop->nSkip;
  pIdx = pLoop->u.btree.pIndex;
  assert( pIdx!=0 );

  /* Figure out how many memory cells we will need then allocate them.
  */
  regBase = pParse->nMem + 1;
  nReg = pLoop->u.btree.nEq + nExtraReg;
  pParse->nMem += nReg;

  zAff = sqlite3DbStrDup(pParse->db, sqlite3IndexAffinityStr(v, pIdx));
  if( !zAff ){
    pParse->db->mallocFailed = 1;
  }

  if( nSkip ){
    int iIdxCur = pLevel->iIdxCur;
    sqlite3VdbeAddOp1(v, (bRev?OP_Last:OP_Rewind), iIdxCur);
    VdbeCoverageIf(v, bRev==0);
    VdbeCoverageIf(v, bRev!=0);
    VdbeComment((v, "begin skip-scan on %s", pIdx->zName));
    j = sqlite3VdbeAddOp0(v, OP_Goto);
    pLevel->addrSkip = sqlite3VdbeAddOp4Int(v, (bRev?OP_SeekLT:OP_SeekGT),
                            iIdxCur, 0, regBase, nSkip);
    VdbeCoverageIf(v, bRev==0);
    VdbeCoverageIf(v, bRev!=0);
    sqlite3VdbeJumpHere(v, j);
    for(j=0; j<nSkip; j++){
      sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, j, regBase+j);
      assert( pIdx->aiColumn[j]>=0 );
      VdbeComment((v, "%s", pIdx->pTable->aCol[pIdx->aiColumn[j]].zName));
    }
  }    

  /* Evaluate the equality constraints
  */
  assert( zAff==0 || (int)strlen(zAff)>=nEq );
  for(j=nSkip; j<nEq; j++){
    int r1;
    pTerm = pLoop->aLTerm[j];
    assert( pTerm!=0 );
    /* The following testcase is true for indices with redundant columns. 
    ** Ex: CREATE INDEX i1 ON t1(a,b,a); SELECT * FROM t1 WHERE a=0 AND b=0; */
    testcase( (pTerm->wtFlags & TERM_CODED)!=0 );
    testcase( pTerm->wtFlags & TERM_VIRTUAL );
    r1 = codeEqualityTerm(pParse, pTerm, pLevel, j, bRev, regBase+j);
    if( r1!=regBase+j ){
      if( nReg==1 ){
        sqlite3ReleaseTempReg(pParse, regBase);
        regBase = r1;
      }else{
        sqlite3VdbeAddOp2(v, OP_SCopy, r1, regBase+j);
      }
    }
    testcase( pTerm->eOperator & WO_ISNULL );
    testcase( pTerm->eOperator & WO_IN );
    if( (pTerm->eOperator & (WO_ISNULL|WO_IN))==0 ){
      Expr *pRight = pTerm->pExpr->pRight;
      if( (pTerm->wtFlags & TERM_IS)==0 && sqlite3ExprCanBeNull(pRight) ){
        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+j, pLevel->addrBrk);
        VdbeCoverage(v);
      }
      if( zAff ){
        if( sqlite3CompareAffinity(pRight, zAff[j])==SQLITE_AFF_BLOB ){
          zAff[j] = SQLITE_AFF_BLOB;
        }
        if( sqlite3ExprNeedsNoAffinityChange(pRight, zAff[j]) ){
          zAff[j] = SQLITE_AFF_BLOB;
        }
      }
    }
  }
  *pzAff = zAff;
  return regBase;
}

#ifndef SQLITE_OMIT_EXPLAIN
/*
** This routine is a helper for explainIndexRange() below
**
** pStr holds the text of an expression that we are building up one term
** at a time.  This routine adds a new term to the end of the expression.
** Terms are separated by AND so add the "AND" text for second and subsequent
** terms only.
*/
static void explainAppendTerm(
  StrAccum *pStr,             /* The text expression being built */
  int iTerm,                  /* Index of this term.  First is zero */
  const char *zColumn,        /* Name of the column */
  const char *zOp             /* Name of the operator */
){
  if( iTerm ) sqlite3StrAccumAppend(pStr, " AND ", 5);
  sqlite3StrAccumAppendAll(pStr, zColumn);
  sqlite3StrAccumAppend(pStr, zOp, 1);
  sqlite3StrAccumAppend(pStr, "?", 1);
}

/*
** Argument pLevel describes a strategy for scanning table pTab. This 
** function appends text to pStr that describes the subset of table
** rows scanned by the strategy in the form of an SQL expression.
**
** For example, if the query:
**
**   SELECT * FROM t1 WHERE a=1 AND b>2;
**
** is run and there is an index on (a, b), then this function returns a
** string similar to:
**
**   "a=? AND b>?"
*/
static void explainIndexRange(StrAccum *pStr, WhereLoop *pLoop, Table *pTab){
  Index *pIndex = pLoop->u.btree.pIndex;
  u16 nEq = pLoop->u.btree.nEq;
  u16 nSkip = pLoop->nSkip;
  int i, j;
  Column *aCol = pTab->aCol;
  i16 *aiColumn = pIndex->aiColumn;

  if( nEq==0 && (pLoop->wsFlags&(WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))==0 ) return;
  sqlite3StrAccumAppend(pStr, " (", 2);
  for(i=0; i<nEq; i++){
    char *z = aiColumn[i] < 0 ? "rowid" : aCol[aiColumn[i]].zName;
    if( i>=nSkip ){
      explainAppendTerm(pStr, i, z, "=");
    }else{
      if( i ) sqlite3StrAccumAppend(pStr, " AND ", 5);
      sqlite3XPrintf(pStr, 0, "ANY(%s)", z);
    }
  }

  j = i;
  if( pLoop->wsFlags&WHERE_BTM_LIMIT ){
    char *z = aiColumn[j] < 0 ? "rowid" : aCol[aiColumn[j]].zName;
    explainAppendTerm(pStr, i++, z, ">");
  }
  if( pLoop->wsFlags&WHERE_TOP_LIMIT ){
    char *z = aiColumn[j] < 0 ? "rowid" : aCol[aiColumn[j]].zName;
    explainAppendTerm(pStr, i, z, "<");
  }
  sqlite3StrAccumAppend(pStr, ")", 1);
}

/*
** This function is a no-op unless currently processing an EXPLAIN QUERY PLAN
** command, or if either SQLITE_DEBUG or SQLITE_ENABLE_STMT_SCANSTATUS was
** defined at compile-time. If it is not a no-op, a single OP_Explain opcode 
** is added to the output to describe the table scan strategy in pLevel.
**
** If an OP_Explain opcode is added to the VM, its address is returned.
** Otherwise, if no OP_Explain is coded, zero is returned.
*/
static int explainOneScan(
  Parse *pParse,                  /* Parse context */
  SrcList *pTabList,              /* Table list this loop refers to */
  WhereLevel *pLevel,             /* Scan to write OP_Explain opcode for */
  int iLevel,                     /* Value for "level" column of output */
  int iFrom,                      /* Value for "from" column of output */
  u16 wctrlFlags                  /* Flags passed to sqlite3WhereBegin() */
){
  int ret = 0;
#if !defined(SQLITE_DEBUG) && !defined(SQLITE_ENABLE_STMT_SCANSTATUS)
  if( pParse->explain==2 )
#endif
  {
    struct SrcList_item *pItem = &pTabList->a[pLevel->iFrom];
    Vdbe *v = pParse->pVdbe;      /* VM being constructed */
    sqlite3 *db = pParse->db;     /* Database handle */
    int iId = pParse->iSelectId;  /* Select id (left-most output column) */
    int isSearch;                 /* True for a SEARCH. False for SCAN. */
    WhereLoop *pLoop;             /* The controlling WhereLoop object */
    u32 flags;                    /* Flags that describe this loop */
    char *zMsg;                   /* Text to add to EQP output */
    StrAccum str;                 /* EQP output string */
    char zBuf[100];               /* Initial space for EQP output string */

    pLoop = pLevel->pWLoop;
    flags = pLoop->wsFlags;
    if( (flags&WHERE_MULTI_OR) || (wctrlFlags&WHERE_ONETABLE_ONLY) ) return 0;

    isSearch = (flags&(WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))!=0
            || ((flags&WHERE_VIRTUALTABLE)==0 && (pLoop->u.btree.nEq>0))
            || (wctrlFlags&(WHERE_ORDERBY_MIN|WHERE_ORDERBY_MAX));

    sqlite3StrAccumInit(&str, db, zBuf, sizeof(zBuf), SQLITE_MAX_LENGTH);
    sqlite3StrAccumAppendAll(&str, isSearch ? "SEARCH" : "SCAN");
    if( pItem->pSelect ){
      sqlite3XPrintf(&str, 0, " SUBQUERY %d", pItem->iSelectId);
    }else{
      sqlite3XPrintf(&str, 0, " TABLE %s", pItem->zName);
    }

    if( pItem->zAlias ){
      sqlite3XPrintf(&str, 0, " AS %s", pItem->zAlias);
    }
    if( (flags & (WHERE_IPK|WHERE_VIRTUALTABLE))==0 ){
      const char *zFmt = 0;
      Index *pIdx;

      assert( pLoop->u.btree.pIndex!=0 );
      pIdx = pLoop->u.btree.pIndex;
      assert( !(flags&WHERE_AUTO_INDEX) || (flags&WHERE_IDX_ONLY) );
      if( !HasRowid(pItem->pTab) && IsPrimaryKeyIndex(pIdx) ){
        if( isSearch ){
          zFmt = "PRIMARY KEY";
        }
      }else if( flags & WHERE_PARTIALIDX ){
        zFmt = "AUTOMATIC PARTIAL COVERING INDEX";
      }else if( flags & WHERE_AUTO_INDEX ){
        zFmt = "AUTOMATIC COVERING INDEX";
      }else if( flags & WHERE_IDX_ONLY ){
        zFmt = "COVERING INDEX %s";
      }else{
        zFmt = "INDEX %s";
      }
      if( zFmt ){
        sqlite3StrAccumAppend(&str, " USING ", 7);
        sqlite3XPrintf(&str, 0, zFmt, pIdx->zName);
        explainIndexRange(&str, pLoop, pItem->pTab);
      }
    }else if( (flags & WHERE_IPK)!=0 && (flags & WHERE_CONSTRAINT)!=0 ){
      const char *zRange;
      if( flags&(WHERE_COLUMN_EQ|WHERE_COLUMN_IN) ){
        zRange = "(rowid=?)";
      }else if( (flags&WHERE_BOTH_LIMIT)==WHERE_BOTH_LIMIT ){
        zRange = "(rowid>? AND rowid<?)";
      }else if( flags&WHERE_BTM_LIMIT ){
        zRange = "(rowid>?)";
      }else{
        assert( flags&WHERE_TOP_LIMIT);
        zRange = "(rowid<?)";
      }
      sqlite3StrAccumAppendAll(&str, " USING INTEGER PRIMARY KEY ");
      sqlite3StrAccumAppendAll(&str, zRange);
    }
#ifndef SQLITE_OMIT_VIRTUALTABLE
    else if( (flags & WHERE_VIRTUALTABLE)!=0 ){
      sqlite3XPrintf(&str, 0, " VIRTUAL TABLE INDEX %d:%s",
                  pLoop->u.vtab.idxNum, pLoop->u.vtab.idxStr);
    }
#endif
#ifdef SQLITE_EXPLAIN_ESTIMATED_ROWS
    if( pLoop->nOut>=10 ){
      sqlite3XPrintf(&str, 0, " (~%llu rows)", sqlite3LogEstToInt(pLoop->nOut));
    }else{
      sqlite3StrAccumAppend(&str, " (~1 row)", 9);
    }
#endif
    zMsg = sqlite3StrAccumFinish(&str);
    ret = sqlite3VdbeAddOp4(v, OP_Explain, iId, iLevel, iFrom, zMsg,P4_DYNAMIC);
  }
  return ret;
}
#else
# define explainOneScan(u,v,w,x,y,z) 0
#endif /* SQLITE_OMIT_EXPLAIN */

#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
/*
** Configure the VM passed as the first argument with an
** sqlite3_stmt_scanstatus() entry corresponding to the scan used to 
** implement level pLvl. Argument pSrclist is a pointer to the FROM 
** clause that the scan reads data from.
**
** If argument addrExplain is not 0, it must be the address of an 
** OP_Explain instruction that describes the same loop.
*/
static void addScanStatus(
  Vdbe *v,                        /* Vdbe to add scanstatus entry to */
  SrcList *pSrclist,              /* FROM clause pLvl reads data from */
  WhereLevel *pLvl,               /* Level to add scanstatus() entry for */
  int addrExplain                 /* Address of OP_Explain (or 0) */
){
  const char *zObj = 0;
  WhereLoop *pLoop = pLvl->pWLoop;
  if( (pLoop->wsFlags & WHERE_VIRTUALTABLE)==0  &&  pLoop->u.btree.pIndex!=0 ){
    zObj = pLoop->u.btree.pIndex->zName;
  }else{
    zObj = pSrclist->a[pLvl->iFrom].zName;
  }
  sqlite3VdbeScanStatus(
      v, addrExplain, pLvl->addrBody, pLvl->addrVisit, pLoop->nOut, zObj
  );
}
#else
# define addScanStatus(a, b, c, d) ((void)d)
#endif

/*
** If the most recently coded instruction is a constant range contraint
** that originated from the LIKE optimization, then change the P3 to be
** pLoop->iLikeRepCntr and set P5.
**
** The LIKE optimization trys to evaluate "x LIKE 'abc%'" as a range
** expression: "x>='ABC' AND x<'abd'".  But this requires that the range
** scan loop run twice, once for strings and a second time for BLOBs.
** The OP_String opcodes on the second pass convert the upper and lower
** bound string contants to blobs.  This routine makes the necessary changes
** to the OP_String opcodes for that to happen.
*/
static void whereLikeOptimizationStringFixup(
  Vdbe *v,                /* prepared statement under construction */
  WhereLevel *pLevel,     /* The loop that contains the LIKE operator */
  WhereTerm *pTerm        /* The upper or lower bound just coded */
){
  if( pTerm->wtFlags & TERM_LIKEOPT ){
    VdbeOp *pOp;
    assert( pLevel->iLikeRepCntr>0 );
    pOp = sqlite3VdbeGetOp(v, -1);
    assert( pOp!=0 );
    assert( pOp->opcode==OP_String8 
            || pTerm->pWC->pWInfo->pParse->db->mallocFailed );
    pOp->p3 = pLevel->iLikeRepCntr;
    pOp->p5 = 1;
  }
}

/*
** Generate code for the start of the iLevel-th loop in the WHERE clause
** implementation described by pWInfo.
*/
static Bitmask codeOneLoopStart(
  WhereInfo *pWInfo,   /* Complete information about the WHERE clause */
  int iLevel,          /* Which level of pWInfo->a[] should be coded */
  Bitmask notReady     /* Which tables are currently available */
){
  int j, k;            /* Loop counters */
  int iCur;            /* The VDBE cursor for the table */
  int addrNxt;         /* Where to jump to continue with the next IN case */
  int omitTable;       /* True if we use the index only */
  int bRev;            /* True if we need to scan in reverse order */
  WhereLevel *pLevel;  /* The where level to be coded */
  WhereLoop *pLoop;    /* The WhereLoop object being coded */
  WhereClause *pWC;    /* Decomposition of the entire WHERE clause */
  WhereTerm *pTerm;               /* A WHERE clause term */
  Parse *pParse;                  /* Parsing context */
  sqlite3 *db;                    /* Database connection */
  Vdbe *v;                        /* The prepared stmt under constructions */
  struct SrcList_item *pTabItem;  /* FROM clause term being coded */
  int addrBrk;                    /* Jump here to break out of the loop */
  int addrCont;                   /* Jump here to continue with next cycle */
  int iRowidReg = 0;        /* Rowid is stored in this register, if not zero */
  int iReleaseReg = 0;      /* Temp register to free before returning */

  pParse = pWInfo->pParse;
  v = pParse->pVdbe;
  pWC = &pWInfo->sWC;
  db = pParse->db;
  pLevel = &pWInfo->a[iLevel];
  pLoop = pLevel->pWLoop;
  pTabItem = &pWInfo->pTabList->a[pLevel->iFrom];
  iCur = pTabItem->iCursor;
  pLevel->notReady = notReady & ~getMask(&pWInfo->sMaskSet, iCur);
  bRev = (pWInfo->revMask>>iLevel)&1;
  omitTable = (pLoop->wsFlags & WHERE_IDX_ONLY)!=0 
           && (pWInfo->wctrlFlags & WHERE_FORCE_TABLE)==0;
  VdbeModuleComment((v, "Begin WHERE-loop%d: %s",iLevel,pTabItem->pTab->zName));

  /* Create labels for the "break" and "continue" instructions
  ** for the current loop.  Jump to addrBrk to break out of a loop.
  ** Jump to cont to go immediately to the next iteration of the
  ** loop.
  **
  ** When there is an IN operator, we also have a "addrNxt" label that
  ** means to continue with the next IN value combination.  When
  ** there are no IN operators in the constraints, the "addrNxt" label
  ** is the same as "addrBrk".
  */
  addrBrk = pLevel->addrBrk = pLevel->addrNxt = sqlite3VdbeMakeLabel(v);
  addrCont = pLevel->addrCont = sqlite3VdbeMakeLabel(v);

  /* If this is the right table of a LEFT OUTER JOIN, allocate and
  ** initialize a memory cell that records if this table matches any
  ** row of the left table of the join.
  */
  if( pLevel->iFrom>0 && (pTabItem[0].jointype & JT_LEFT)!=0 ){
    pLevel->iLeftJoin = ++pParse->nMem;
    sqlite3VdbeAddOp2(v, OP_Integer, 0, pLevel->iLeftJoin);
    VdbeComment((v, "init LEFT JOIN no-match flag"));
  }

  /* Special case of a FROM clause subquery implemented as a co-routine */
  if( pTabItem->viaCoroutine ){
    int regYield = pTabItem->regReturn;
    sqlite3VdbeAddOp3(v, OP_InitCoroutine, regYield, 0, pTabItem->addrFillSub);
    pLevel->p2 =  sqlite3VdbeAddOp2(v, OP_Yield, regYield, addrBrk);
    VdbeCoverage(v);
    VdbeComment((v, "next row of \"%s\"", pTabItem->pTab->zName));
    pLevel->op = OP_Goto;
  }else

#ifndef SQLITE_OMIT_VIRTUALTABLE
  if(  (pLoop->wsFlags & WHERE_VIRTUALTABLE)!=0 ){
    /* Case 1:  The table is a virtual-table.  Use the VFilter and VNext
    **          to access the data.
    */
    int iReg;   /* P3 Value for OP_VFilter */
    int addrNotFound;
    int nConstraint = pLoop->nLTerm;

    sqlite3ExprCachePush(pParse);
    iReg = sqlite3GetTempRange(pParse, nConstraint+2);
    addrNotFound = pLevel->addrBrk;
    for(j=0; j<nConstraint; j++){
      int iTarget = iReg+j+2;
      pTerm = pLoop->aLTerm[j];
      if( pTerm==0 ) continue;
      if( pTerm->eOperator & WO_IN ){
        codeEqualityTerm(pParse, pTerm, pLevel, j, bRev, iTarget);
        addrNotFound = pLevel->addrNxt;
      }else{
        sqlite3ExprCode(pParse, pTerm->pExpr->pRight, iTarget);
      }
    }
    sqlite3VdbeAddOp2(v, OP_Integer, pLoop->u.vtab.idxNum, iReg);
    sqlite3VdbeAddOp2(v, OP_Integer, nConstraint, iReg+1);
    sqlite3VdbeAddOp4(v, OP_VFilter, iCur, addrNotFound, iReg,
                      pLoop->u.vtab.idxStr,
                      pLoop->u.vtab.needFree ? P4_MPRINTF : P4_STATIC);
    VdbeCoverage(v);
    pLoop->u.vtab.needFree = 0;
    for(j=0; j<nConstraint && j<16; j++){
      if( (pLoop->u.vtab.omitMask>>j)&1 ){
        disableTerm(pLevel, pLoop->aLTerm[j]);
      }
    }
    pLevel->op = OP_VNext;
    pLevel->p1 = iCur;
    pLevel->p2 = sqlite3VdbeCurrentAddr(v);
    sqlite3ReleaseTempRange(pParse, iReg, nConstraint+2);
    sqlite3ExprCachePop(pParse);
  }else
#endif /* SQLITE_OMIT_VIRTUALTABLE */

  if( (pLoop->wsFlags & WHERE_IPK)!=0
   && (pLoop->wsFlags & (WHERE_COLUMN_IN|WHERE_COLUMN_EQ))!=0
  ){
    /* Case 2:  We can directly reference a single row using an
    **          equality comparison against the ROWID field.  Or
    **          we reference multiple rows using a "rowid IN (...)"
    **          construct.
    */
    assert( pLoop->u.btree.nEq==1 );
    pTerm = pLoop->aLTerm[0];
    assert( pTerm!=0 );
    assert( pTerm->pExpr!=0 );
    assert( omitTable==0 );
    testcase( pTerm->wtFlags & TERM_VIRTUAL );
    iReleaseReg = ++pParse->nMem;
    iRowidReg = codeEqualityTerm(pParse, pTerm, pLevel, 0, bRev, iReleaseReg);
    if( iRowidReg!=iReleaseReg ) sqlite3ReleaseTempReg(pParse, iReleaseReg);
    addrNxt = pLevel->addrNxt;
    sqlite3VdbeAddOp2(v, OP_MustBeInt, iRowidReg, addrNxt); VdbeCoverage(v);
    sqlite3VdbeAddOp3(v, OP_NotExists, iCur, addrNxt, iRowidReg);
    VdbeCoverage(v);
    sqlite3ExprCacheAffinityChange(pParse, iRowidReg, 1);
    sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
    VdbeComment((v, "pk"));
    pLevel->op = OP_Noop;
  }else if( (pLoop->wsFlags & WHERE_IPK)!=0
         && (pLoop->wsFlags & WHERE_COLUMN_RANGE)!=0
  ){
    /* Case 3:  We have an inequality comparison against the ROWID field.
    */
    int testOp = OP_Noop;
    int start;
    int memEndValue = 0;
    WhereTerm *pStart, *pEnd;

    assert( omitTable==0 );
    j = 0;
    pStart = pEnd = 0;
    if( pLoop->wsFlags & WHERE_BTM_LIMIT ) pStart = pLoop->aLTerm[j++];
    if( pLoop->wsFlags & WHERE_TOP_LIMIT ) pEnd = pLoop->aLTerm[j++];
    assert( pStart!=0 || pEnd!=0 );
    if( bRev ){
      pTerm = pStart;
      pStart = pEnd;
      pEnd = pTerm;
    }
    if( pStart ){
      Expr *pX;             /* The expression that defines the start bound */
      int r1, rTemp;        /* Registers for holding the start boundary */

      /* The following constant maps TK_xx codes into corresponding 
      ** seek opcodes.  It depends on a particular ordering of TK_xx
      */
      const u8 aMoveOp[] = {
           /* TK_GT */  OP_SeekGT,
           /* TK_LE */  OP_SeekLE,
           /* TK_LT */  OP_SeekLT,
           /* TK_GE */  OP_SeekGE
      };
      assert( TK_LE==TK_GT+1 );      /* Make sure the ordering.. */
      assert( TK_LT==TK_GT+2 );      /*  ... of the TK_xx values... */
      assert( TK_GE==TK_GT+3 );      /*  ... is correcct. */

      assert( (pStart->wtFlags & TERM_VNULL)==0 );
      testcase( pStart->wtFlags & TERM_VIRTUAL );
      pX = pStart->pExpr;
      assert( pX!=0 );
      testcase( pStart->leftCursor!=iCur ); /* transitive constraints */
      r1 = sqlite3ExprCodeTemp(pParse, pX->pRight, &rTemp);
      sqlite3VdbeAddOp3(v, aMoveOp[pX->op-TK_GT], iCur, addrBrk, r1);
      VdbeComment((v, "pk"));
      VdbeCoverageIf(v, pX->op==TK_GT);
      VdbeCoverageIf(v, pX->op==TK_LE);
      VdbeCoverageIf(v, pX->op==TK_LT);
      VdbeCoverageIf(v, pX->op==TK_GE);
      sqlite3ExprCacheAffinityChange(pParse, r1, 1);
      sqlite3ReleaseTempReg(pParse, rTemp);
      disableTerm(pLevel, pStart);
    }else{
      sqlite3VdbeAddOp2(v, bRev ? OP_Last : OP_Rewind, iCur, addrBrk);
      VdbeCoverageIf(v, bRev==0);
      VdbeCoverageIf(v, bRev!=0);
    }
    if( pEnd ){
      Expr *pX;
      pX = pEnd->pExpr;
      assert( pX!=0 );
      assert( (pEnd->wtFlags & TERM_VNULL)==0 );
      testcase( pEnd->leftCursor!=iCur ); /* Transitive constraints */
      testcase( pEnd->wtFlags & TERM_VIRTUAL );
      memEndValue = ++pParse->nMem;
      sqlite3ExprCode(pParse, pX->pRight, memEndValue);
      if( pX->op==TK_LT || pX->op==TK_GT ){
        testOp = bRev ? OP_Le : OP_Ge;
      }else{
        testOp = bRev ? OP_Lt : OP_Gt;
      }
      disableTerm(pLevel, pEnd);
    }
    start = sqlite3VdbeCurrentAddr(v);
    pLevel->op = bRev ? OP_Prev : OP_Next;
    pLevel->p1 = iCur;
    pLevel->p2 = start;
    assert( pLevel->p5==0 );
    if( testOp!=OP_Noop ){
      iRowidReg = ++pParse->nMem;
      sqlite3VdbeAddOp2(v, OP_Rowid, iCur, iRowidReg);
      sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
      sqlite3VdbeAddOp3(v, testOp, memEndValue, addrBrk, iRowidReg);
      VdbeCoverageIf(v, testOp==OP_Le);
      VdbeCoverageIf(v, testOp==OP_Lt);
      VdbeCoverageIf(v, testOp==OP_Ge);
      VdbeCoverageIf(v, testOp==OP_Gt);
      sqlite3VdbeChangeP5(v, SQLITE_AFF_NUMERIC | SQLITE_JUMPIFNULL);
    }
  }else if( pLoop->wsFlags & WHERE_INDEXED ){
    /* Case 4: A scan using an index.
    **
    **         The WHERE clause may contain zero or more equality 
    **         terms ("==" or "IN" operators) that refer to the N
    **         left-most columns of the index. It may also contain
    **         inequality constraints (>, <, >= or <=) on the indexed
    **         column that immediately follows the N equalities. Only 
    **         the right-most column can be an inequality - the rest must
    **         use the "==" and "IN" operators. For example, if the 
    **         index is on (x,y,z), then the following clauses are all 
    **         optimized:
    **
    **            x=5
    **            x=5 AND y=10
    **            x=5 AND y<10
    **            x=5 AND y>5 AND y<10
    **            x=5 AND y=5 AND z<=10
    **
    **         The z<10 term of the following cannot be used, only
    **         the x=5 term:
    **
    **            x=5 AND z<10
    **
    **         N may be zero if there are inequality constraints.
    **         If there are no inequality constraints, then N is at
    **         least one.
    **
    **         This case is also used when there are no WHERE clause
    **         constraints but an index is selected anyway, in order
    **         to force the output order to conform to an ORDER BY.
    */  
    static const u8 aStartOp[] = {
      0,
      0,
      OP_Rewind,           /* 2: (!start_constraints && startEq &&  !bRev) */
      OP_Last,             /* 3: (!start_constraints && startEq &&   bRev) */
      OP_SeekGT,           /* 4: (start_constraints  && !startEq && !bRev) */
      OP_SeekLT,           /* 5: (start_constraints  && !startEq &&  bRev) */
      OP_SeekGE,           /* 6: (start_constraints  &&  startEq && !bRev) */
      OP_SeekLE            /* 7: (start_constraints  &&  startEq &&  bRev) */
    };
    static const u8 aEndOp[] = {
      OP_IdxGE,            /* 0: (end_constraints && !bRev && !endEq) */
      OP_IdxGT,            /* 1: (end_constraints && !bRev &&  endEq) */
      OP_IdxLE,            /* 2: (end_constraints &&  bRev && !endEq) */
      OP_IdxLT,            /* 3: (end_constraints &&  bRev &&  endEq) */
    };
    u16 nEq = pLoop->u.btree.nEq;     /* Number of == or IN terms */
    int regBase;                 /* Base register holding constraint values */
    WhereTerm *pRangeStart = 0;  /* Inequality constraint at range start */
    WhereTerm *pRangeEnd = 0;    /* Inequality constraint at range end */
    int startEq;                 /* True if range start uses ==, >= or <= */
    int endEq;                   /* True if range end uses ==, >= or <= */
    int start_constraints;       /* Start of range is constrained */
    int nConstraint;             /* Number of constraint terms */
    Index *pIdx;                 /* The index we will be using */
    int iIdxCur;                 /* The VDBE cursor for the index */
    int nExtraReg = 0;           /* Number of extra registers needed */
    int op;                      /* Instruction opcode */
    char *zStartAff;             /* Affinity for start of range constraint */
    char cEndAff = 0;            /* Affinity for end of range constraint */
    u8 bSeekPastNull = 0;        /* True to seek past initial nulls */
    u8 bStopAtNull = 0;          /* Add condition to terminate at NULLs */

    pIdx = pLoop->u.btree.pIndex;
    iIdxCur = pLevel->iIdxCur;
    assert( nEq>=pLoop->nSkip );

    /* If this loop satisfies a sort order (pOrderBy) request that 
    ** was passed to this function to implement a "SELECT min(x) ..." 
    ** query, then the caller will only allow the loop to run for
    ** a single iteration. This means that the first row returned
    ** should not have a NULL value stored in 'x'. If column 'x' is
    ** the first one after the nEq equality constraints in the index,
    ** this requires some special handling.
    */
    assert( pWInfo->pOrderBy==0
         || pWInfo->pOrderBy->nExpr==1
         || (pWInfo->wctrlFlags&WHERE_ORDERBY_MIN)==0 );
    if( (pWInfo->wctrlFlags&WHERE_ORDERBY_MIN)!=0
     && pWInfo->nOBSat>0
     && (pIdx->nKeyCol>nEq)
    ){
      assert( pLoop->nSkip==0 );
      bSeekPastNull = 1;
      nExtraReg = 1;
    }

    /* Find any inequality constraint terms for the start and end 
    ** of the range. 
    */
    j = nEq;
    if( pLoop->wsFlags & WHERE_BTM_LIMIT ){
      pRangeStart = pLoop->aLTerm[j++];
      nExtraReg = 1;
      /* Like optimization range constraints always occur in pairs */
      assert( (pRangeStart->wtFlags & TERM_LIKEOPT)==0 || 
              (pLoop->wsFlags & WHERE_TOP_LIMIT)!=0 );
    }
    if( pLoop->wsFlags & WHERE_TOP_LIMIT ){
      pRangeEnd = pLoop->aLTerm[j++];
      nExtraReg = 1;
      if( (pRangeEnd->wtFlags & TERM_LIKEOPT)!=0 ){
        assert( pRangeStart!=0 );                     /* LIKE opt constraints */
        assert( pRangeStart->wtFlags & TERM_LIKEOPT );   /* occur in pairs */
        pLevel->iLikeRepCntr = ++pParse->nMem;
        testcase( bRev );
        testcase( pIdx->aSortOrder[nEq]==SQLITE_SO_DESC );
        sqlite3VdbeAddOp2(v, OP_Integer,
                          bRev ^ (pIdx->aSortOrder[nEq]==SQLITE_SO_DESC),
                          pLevel->iLikeRepCntr);
        VdbeComment((v, "LIKE loop counter"));
        pLevel->addrLikeRep = sqlite3VdbeCurrentAddr(v);
      }
      if( pRangeStart==0
       && (j = pIdx->aiColumn[nEq])>=0 
       && pIdx->pTable->aCol[j].notNull==0
      ){
        bSeekPastNull = 1;
      }
    }
    assert( pRangeEnd==0 || (pRangeEnd->wtFlags & TERM_VNULL)==0 );

    /* Generate code to evaluate all constraint terms using == or IN
    ** and store the values of those terms in an array of registers
    ** starting at regBase.
    */
    regBase = codeAllEqualityTerms(pParse,pLevel,bRev,nExtraReg,&zStartAff);
    assert( zStartAff==0 || sqlite3Strlen30(zStartAff)>=nEq );
    if( zStartAff ) cEndAff = zStartAff[nEq];
    addrNxt = pLevel->addrNxt;

    /* If we are doing a reverse order scan on an ascending index, or
    ** a forward order scan on a descending index, interchange the 
    ** start and end terms (pRangeStart and pRangeEnd).
    */
    if( (nEq<pIdx->nKeyCol && bRev==(pIdx->aSortOrder[nEq]==SQLITE_SO_ASC))
     || (bRev && pIdx->nKeyCol==nEq)
    ){
      SWAP(WhereTerm *, pRangeEnd, pRangeStart);
      SWAP(u8, bSeekPastNull, bStopAtNull);
    }

    testcase( pRangeStart && (pRangeStart->eOperator & WO_LE)!=0 );
    testcase( pRangeStart && (pRangeStart->eOperator & WO_GE)!=0 );
    testcase( pRangeEnd && (pRangeEnd->eOperator & WO_LE)!=0 );
    testcase( pRangeEnd && (pRangeEnd->eOperator & WO_GE)!=0 );
    startEq = !pRangeStart || pRangeStart->eOperator & (WO_LE|WO_GE);
    endEq =   !pRangeEnd || pRangeEnd->eOperator & (WO_LE|WO_GE);
    start_constraints = pRangeStart || nEq>0;

    /* Seek the index cursor to the start of the range. */
    nConstraint = nEq;
    if( pRangeStart ){
      Expr *pRight = pRangeStart->pExpr->pRight;
      sqlite3ExprCode(pParse, pRight, regBase+nEq);
      whereLikeOptimizationStringFixup(v, pLevel, pRangeStart);
      if( (pRangeStart->wtFlags & TERM_VNULL)==0
       && sqlite3ExprCanBeNull(pRight)
      ){
        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
        VdbeCoverage(v);
      }
      if( zStartAff ){
        if( sqlite3CompareAffinity(pRight, zStartAff[nEq])==SQLITE_AFF_BLOB){
          /* Since the comparison is to be performed with no conversions
          ** applied to the operands, set the affinity to apply to pRight to 
          ** SQLITE_AFF_BLOB.  */
          zStartAff[nEq] = SQLITE_AFF_BLOB;
        }
        if( sqlite3ExprNeedsNoAffinityChange(pRight, zStartAff[nEq]) ){
          zStartAff[nEq] = SQLITE_AFF_BLOB;
        }
      }  
      nConstraint++;
      testcase( pRangeStart->wtFlags & TERM_VIRTUAL );
    }else if( bSeekPastNull ){
      sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
      nConstraint++;
      startEq = 0;
      start_constraints = 1;
    }
    codeApplyAffinity(pParse, regBase, nConstraint - bSeekPastNull, zStartAff);
    op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
    assert( op!=0 );
    sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
    VdbeCoverage(v);
    VdbeCoverageIf(v, op==OP_Rewind);  testcase( op==OP_Rewind );
    VdbeCoverageIf(v, op==OP_Last);    testcase( op==OP_Last );
    VdbeCoverageIf(v, op==OP_SeekGT);  testcase( op==OP_SeekGT );
    VdbeCoverageIf(v, op==OP_SeekGE);  testcase( op==OP_SeekGE );
    VdbeCoverageIf(v, op==OP_SeekLE);  testcase( op==OP_SeekLE );
    VdbeCoverageIf(v, op==OP_SeekLT);  testcase( op==OP_SeekLT );

    /* Load the value for the inequality constraint at the end of the
    ** range (if any).
    */
    nConstraint = nEq;
    if( pRangeEnd ){
      Expr *pRight = pRangeEnd->pExpr->pRight;
      sqlite3ExprCacheRemove(pParse, regBase+nEq, 1);
      sqlite3ExprCode(pParse, pRight, regBase+nEq);
      whereLikeOptimizationStringFixup(v, pLevel, pRangeEnd);
      if( (pRangeEnd->wtFlags & TERM_VNULL)==0
       && sqlite3ExprCanBeNull(pRight)
      ){
        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
        VdbeCoverage(v);
      }
      if( sqlite3CompareAffinity(pRight, cEndAff)!=SQLITE_AFF_BLOB
       && !sqlite3ExprNeedsNoAffinityChange(pRight, cEndAff)
      ){
        codeApplyAffinity(pParse, regBase+nEq, 1, &cEndAff);
      }
      nConstraint++;
      testcase( pRangeEnd->wtFlags & TERM_VIRTUAL );
    }else if( bStopAtNull ){
      sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
      endEq = 0;
      nConstraint++;
    }
    sqlite3DbFree(db, zStartAff);

    /* Top of the loop body */
    pLevel->p2 = sqlite3VdbeCurrentAddr(v);

    /* Check if the index cursor is past the end of the range. */
    if( nConstraint ){
      op = aEndOp[bRev*2 + endEq];
      sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
      testcase( op==OP_IdxGT );  VdbeCoverageIf(v, op==OP_IdxGT );
      testcase( op==OP_IdxGE );  VdbeCoverageIf(v, op==OP_IdxGE );
      testcase( op==OP_IdxLT );  VdbeCoverageIf(v, op==OP_IdxLT );
      testcase( op==OP_IdxLE );  VdbeCoverageIf(v, op==OP_IdxLE );
    }

    /* Seek the table cursor, if required */
    disableTerm(pLevel, pRangeStart);
    disableTerm(pLevel, pRangeEnd);
    if( omitTable ){
      /* pIdx is a covering index.  No need to access the main table. */
    }else if( HasRowid(pIdx->pTable) ){
      iRowidReg = ++pParse->nMem;
      sqlite3VdbeAddOp2(v, OP_IdxRowid, iIdxCur, iRowidReg);
      sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
      sqlite3VdbeAddOp2(v, OP_Seek, iCur, iRowidReg);  /* Deferred seek */
    }else if( iCur!=iIdxCur ){
      Index *pPk = sqlite3PrimaryKeyIndex(pIdx->pTable);
      iRowidReg = sqlite3GetTempRange(pParse, pPk->nKeyCol);
      for(j=0; j<pPk->nKeyCol; j++){
        k = sqlite3ColumnOfIndex(pIdx, pPk->aiColumn[j]);
        sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, k, iRowidReg+j);
      }
      sqlite3VdbeAddOp4Int(v, OP_NotFound, iCur, addrCont,
                           iRowidReg, pPk->nKeyCol); VdbeCoverage(v);
    }

    /* Record the instruction used to terminate the loop. Disable 
    ** WHERE clause terms made redundant by the index range scan.
    */
    if( pLoop->wsFlags & WHERE_ONEROW ){
      pLevel->op = OP_Noop;
    }else if( bRev ){
      pLevel->op = OP_Prev;
    }else{
      pLevel->op = OP_Next;
    }
    pLevel->p1 = iIdxCur;
    pLevel->p3 = (pLoop->wsFlags&WHERE_UNQ_WANTED)!=0 ? 1:0;
    if( (pLoop->wsFlags & WHERE_CONSTRAINT)==0 ){
      pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
    }else{
      assert( pLevel->p5==0 );
    }
  }else

#ifndef SQLITE_OMIT_OR_OPTIMIZATION
  if( pLoop->wsFlags & WHERE_MULTI_OR ){
    /* Case 5:  Two or more separately indexed terms connected by OR
    **
    ** Example:
    **
    **   CREATE TABLE t1(a,b,c,d);
    **   CREATE INDEX i1 ON t1(a);
    **   CREATE INDEX i2 ON t1(b);
    **   CREATE INDEX i3 ON t1(c);
    **
    **   SELECT * FROM t1 WHERE a=5 OR b=7 OR (c=11 AND d=13)
    **
    ** In the example, there are three indexed terms connected by OR.
    ** The top of the loop looks like this:
    **
    **          Null       1                # Zero the rowset in reg 1
    **
    ** Then, for each indexed term, the following. The arguments to
    ** RowSetTest are such that the rowid of the current row is inserted
    ** into the RowSet. If it is already present, control skips the
    ** Gosub opcode and jumps straight to the code generated by WhereEnd().
    **
    **        sqlite3WhereBegin(<term>)
    **          RowSetTest                  # Insert rowid into rowset
    **          Gosub      2 A
    **        sqlite3WhereEnd()
    **
    ** Following the above, code to terminate the loop. Label A, the target
    ** of the Gosub above, jumps to the instruction right after the Goto.
    **
    **          Null       1                # Zero the rowset in reg 1
    **          Goto       B                # The loop is finished.
    **
    **       A: <loop body>                 # Return data, whatever.
    **
    **          Return     2                # Jump back to the Gosub
    **
    **       B: <after the loop>
    **
    ** Added 2014-05-26: If the table is a WITHOUT ROWID table, then
    ** use an ephemeral index instead of a RowSet to record the primary
    ** keys of the rows we have already seen.
    **
    */
    WhereClause *pOrWc;    /* The OR-clause broken out into subterms */
    SrcList *pOrTab;       /* Shortened table list or OR-clause generation */
    Index *pCov = 0;             /* Potential covering index (or NULL) */
    int iCovCur = pParse->nTab++;  /* Cursor used for index scans (if any) */

    int regReturn = ++pParse->nMem;           /* Register used with OP_Gosub */
    int regRowset = 0;                        /* Register for RowSet object */
    int regRowid = 0;                         /* Register holding rowid */
    int iLoopBody = sqlite3VdbeMakeLabel(v);  /* Start of loop body */
    int iRetInit;                             /* Address of regReturn init */
    int untestedTerms = 0;             /* Some terms not completely tested */
    int ii;                            /* Loop counter */
    u16 wctrlFlags;                    /* Flags for sub-WHERE clause */
    Expr *pAndExpr = 0;                /* An ".. AND (...)" expression */
    Table *pTab = pTabItem->pTab;
   
    pTerm = pLoop->aLTerm[0];
    assert( pTerm!=0 );
    assert( pTerm->eOperator & WO_OR );
    assert( (pTerm->wtFlags & TERM_ORINFO)!=0 );
    pOrWc = &pTerm->u.pOrInfo->wc;
    pLevel->op = OP_Return;
    pLevel->p1 = regReturn;

    /* Set up a new SrcList in pOrTab containing the table being scanned
    ** by this loop in the a[0] slot and all notReady tables in a[1..] slots.
    ** This becomes the SrcList in the recursive call to sqlite3WhereBegin().
    */
    if( pWInfo->nLevel>1 ){
      int nNotReady;                 /* The number of notReady tables */
      struct SrcList_item *origSrc;     /* Original list of tables */
      nNotReady = pWInfo->nLevel - iLevel - 1;
      pOrTab = sqlite3StackAllocRaw(db,
                            sizeof(*pOrTab)+ nNotReady*sizeof(pOrTab->a[0]));
      if( pOrTab==0 ) return notReady;
      pOrTab->nAlloc = (u8)(nNotReady + 1);
      pOrTab->nSrc = pOrTab->nAlloc;
      memcpy(pOrTab->a, pTabItem, sizeof(*pTabItem));
      origSrc = pWInfo->pTabList->a;
      for(k=1; k<=nNotReady; k++){
        memcpy(&pOrTab->a[k], &origSrc[pLevel[k].iFrom], sizeof(pOrTab->a[k]));
      }
    }else{
      pOrTab = pWInfo->pTabList;
    }

    /* Initialize the rowset register to contain NULL. An SQL NULL is 
    ** equivalent to an empty rowset.  Or, create an ephemeral index
    ** capable of holding primary keys in the case of a WITHOUT ROWID.
    **
    ** Also initialize regReturn to contain the address of the instruction 
    ** immediately following the OP_Return at the bottom of the loop. This
    ** is required in a few obscure LEFT JOIN cases where control jumps
    ** over the top of the loop into the body of it. In this case the 
    ** correct response for the end-of-loop code (the OP_Return) is to 
    ** fall through to the next instruction, just as an OP_Next does if
    ** called on an uninitialized cursor.
    */
    if( (pWInfo->wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
      if( HasRowid(pTab) ){
        regRowset = ++pParse->nMem;
        sqlite3VdbeAddOp2(v, OP_Null, 0, regRowset);
      }else{
        Index *pPk = sqlite3PrimaryKeyIndex(pTab);
        regRowset = pParse->nTab++;
        sqlite3VdbeAddOp2(v, OP_OpenEphemeral, regRowset, pPk->nKeyCol);
        sqlite3VdbeSetP4KeyInfo(pParse, pPk);
      }
      regRowid = ++pParse->nMem;
    }
    iRetInit = sqlite3VdbeAddOp2(v, OP_Integer, 0, regReturn);

    /* If the original WHERE clause is z of the form:  (x1 OR x2 OR ...) AND y
    ** Then for every term xN, evaluate as the subexpression: xN AND z
    ** That way, terms in y that are factored into the disjunction will
    ** be picked up by the recursive calls to sqlite3WhereBegin() below.
    **
    ** Actually, each subexpression is converted to "xN AND w" where w is
    ** the "interesting" terms of z - terms that did not originate in the
    ** ON or USING clause of a LEFT JOIN, and terms that are usable as 
    ** indices.
    **
    ** This optimization also only applies if the (x1 OR x2 OR ...) term
    ** is not contained in the ON clause of a LEFT JOIN.
    ** See ticket http://www.sqlite.org/src/info/f2369304e4
    */
    if( pWC->nTerm>1 ){
      int iTerm;
      for(iTerm=0; iTerm<pWC->nTerm; iTerm++){
        Expr *pExpr = pWC->a[iTerm].pExpr;
        if( &pWC->a[iTerm] == pTerm ) continue;
        if( ExprHasProperty(pExpr, EP_FromJoin) ) continue;
        if( (pWC->a[iTerm].wtFlags & TERM_VIRTUAL)!=0 ) continue;
        if( (pWC->a[iTerm].eOperator & WO_ALL)==0 ) continue;
        testcase( pWC->a[iTerm].wtFlags & TERM_ORINFO );
        pExpr = sqlite3ExprDup(db, pExpr, 0);
        pAndExpr = sqlite3ExprAnd(db, pAndExpr, pExpr);
      }
      if( pAndExpr ){
        pAndExpr = sqlite3PExpr(pParse, TK_AND, 0, pAndExpr, 0);
      }
    }

    /* Run a separate WHERE clause for each term of the OR clause.  After
    ** eliminating duplicates from other WHERE clauses, the action for each
    ** sub-WHERE clause is to to invoke the main loop body as a subroutine.
    */
    wctrlFlags =  WHERE_OMIT_OPEN_CLOSE
                | WHERE_FORCE_TABLE
                | WHERE_ONETABLE_ONLY
                | WHERE_NO_AUTOINDEX;
    for(ii=0; ii<pOrWc->nTerm; ii++){
      WhereTerm *pOrTerm = &pOrWc->a[ii];
      if( pOrTerm->leftCursor==iCur || (pOrTerm->eOperator & WO_AND)!=0 ){
        WhereInfo *pSubWInfo;           /* Info for single OR-term scan */
        Expr *pOrExpr = pOrTerm->pExpr; /* Current OR clause term */
        int j1 = 0;                     /* Address of jump operation */
        if( pAndExpr && !ExprHasProperty(pOrExpr, EP_FromJoin) ){
          pAndExpr->pLeft = pOrExpr;
          pOrExpr = pAndExpr;
        }
        /* Loop through table entries that match term pOrTerm. */
        WHERETRACE(0xffff, ("Subplan for OR-clause:\n"));
        pSubWInfo = sqlite3WhereBegin(pParse, pOrTab, pOrExpr, 0, 0,
                                      wctrlFlags, iCovCur);
        assert( pSubWInfo || pParse->nErr || db->mallocFailed );
        if( pSubWInfo ){
          WhereLoop *pSubLoop;
          int addrExplain = explainOneScan(
              pParse, pOrTab, &pSubWInfo->a[0], iLevel, pLevel->iFrom, 0
          );
          addScanStatus(v, pOrTab, &pSubWInfo->a[0], addrExplain);

          /* This is the sub-WHERE clause body.  First skip over
          ** duplicate rows from prior sub-WHERE clauses, and record the
          ** rowid (or PRIMARY KEY) for the current row so that the same
          ** row will be skipped in subsequent sub-WHERE clauses.
          */
          if( (pWInfo->wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
            int r;
            int iSet = ((ii==pOrWc->nTerm-1)?-1:ii);
            if( HasRowid(pTab) ){
              r = sqlite3ExprCodeGetColumn(pParse, pTab, -1, iCur, regRowid, 0);
              j1 = sqlite3VdbeAddOp4Int(v, OP_RowSetTest, regRowset, 0, r,iSet);
              VdbeCoverage(v);
            }else{
              Index *pPk = sqlite3PrimaryKeyIndex(pTab);
              int nPk = pPk->nKeyCol;
              int iPk;

              /* Read the PK into an array of temp registers. */
              r = sqlite3GetTempRange(pParse, nPk);
              for(iPk=0; iPk<nPk; iPk++){
                int iCol = pPk->aiColumn[iPk];
                sqlite3ExprCodeGetColumn(pParse, pTab, iCol, iCur, r+iPk, 0);
              }

              /* Check if the temp table already contains this key. If so,
              ** the row has already been included in the result set and
              ** can be ignored (by jumping past the Gosub below). Otherwise,
              ** insert the key into the temp table and proceed with processing
              ** the row.
              **
              ** Use some of the same optimizations as OP_RowSetTest: If iSet
              ** is zero, assume that the key cannot already be present in
              ** the temp table. And if iSet is -1, assume that there is no 
              ** need to insert the key into the temp table, as it will never 
              ** be tested for.  */ 
              if( iSet ){
                j1 = sqlite3VdbeAddOp4Int(v, OP_Found, regRowset, 0, r, nPk);
                VdbeCoverage(v);
              }
              if( iSet>=0 ){
                sqlite3VdbeAddOp3(v, OP_MakeRecord, r, nPk, regRowid);
                sqlite3VdbeAddOp3(v, OP_IdxInsert, regRowset, regRowid, 0);
                if( iSet ) sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
              }

              /* Release the array of temp registers */
              sqlite3ReleaseTempRange(pParse, r, nPk);
            }
          }

          /* Invoke the main loop body as a subroutine */
          sqlite3VdbeAddOp2(v, OP_Gosub, regReturn, iLoopBody);

          /* Jump here (skipping the main loop body subroutine) if the
          ** current sub-WHERE row is a duplicate from prior sub-WHEREs. */
          if( j1 ) sqlite3VdbeJumpHere(v, j1);

          /* The pSubWInfo->untestedTerms flag means that this OR term
          ** contained one or more AND term from a notReady table.  The
          ** terms from the notReady table could not be tested and will
          ** need to be tested later.
          */
          if( pSubWInfo->untestedTerms ) untestedTerms = 1;

          /* If all of the OR-connected terms are optimized using the same
          ** index, and the index is opened using the same cursor number
          ** by each call to sqlite3WhereBegin() made by this loop, it may
          ** be possible to use that index as a covering index.
          **
          ** If the call to sqlite3WhereBegin() above resulted in a scan that
          ** uses an index, and this is either the first OR-connected term
          ** processed or the index is the same as that used by all previous
          ** terms, set pCov to the candidate covering index. Otherwise, set 
          ** pCov to NULL to indicate that no candidate covering index will 
          ** be available.
          */
          pSubLoop = pSubWInfo->a[0].pWLoop;
          assert( (pSubLoop->wsFlags & WHERE_AUTO_INDEX)==0 );
          if( (pSubLoop->wsFlags & WHERE_INDEXED)!=0
           && (ii==0 || pSubLoop->u.btree.pIndex==pCov)
           && (HasRowid(pTab) || !IsPrimaryKeyIndex(pSubLoop->u.btree.pIndex))
          ){
            assert( pSubWInfo->a[0].iIdxCur==iCovCur );
            pCov = pSubLoop->u.btree.pIndex;
            wctrlFlags |= WHERE_REOPEN_IDX;
          }else{
            pCov = 0;
          }

          /* Finish the loop through table entries that match term pOrTerm. */
          sqlite3WhereEnd(pSubWInfo);
        }
      }
    }
    pLevel->u.pCovidx = pCov;
    if( pCov ) pLevel->iIdxCur = iCovCur;
    if( pAndExpr ){
      pAndExpr->pLeft = 0;
      sqlite3ExprDelete(db, pAndExpr);
    }
    sqlite3VdbeChangeP1(v, iRetInit, sqlite3VdbeCurrentAddr(v));
    sqlite3VdbeAddOp2(v, OP_Goto, 0, pLevel->addrBrk);
    sqlite3VdbeResolveLabel(v, iLoopBody);

    if( pWInfo->nLevel>1 ) sqlite3StackFree(db, pOrTab);
    if( !untestedTerms ) disableTerm(pLevel, pTerm);
  }else
#endif /* SQLITE_OMIT_OR_OPTIMIZATION */

  {
    /* Case 6:  There is no usable index.  We must do a complete
    **          scan of the entire table.
    */
    static const u8 aStep[] = { OP_Next, OP_Prev };
    static const u8 aStart[] = { OP_Rewind, OP_Last };
    assert( bRev==0 || bRev==1 );
    if( pTabItem->isRecursive ){
      /* Tables marked isRecursive have only a single row that is stored in
      ** a pseudo-cursor.  No need to Rewind or Next such cursors. */
      pLevel->op = OP_Noop;
    }else{
      pLevel->op = aStep[bRev];
      pLevel->p1 = iCur;
      pLevel->p2 = 1 + sqlite3VdbeAddOp2(v, aStart[bRev], iCur, addrBrk);
      VdbeCoverageIf(v, bRev==0);
      VdbeCoverageIf(v, bRev!=0);
      pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
    }
  }

#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
  pLevel->addrVisit = sqlite3VdbeCurrentAddr(v);
#endif

  /* Insert code to test every subexpression that can be completely
  ** computed using the current set of tables.
  */
  for(pTerm=pWC->a, j=pWC->nTerm; j>0; j--, pTerm++){
    Expr *pE;
    int skipLikeAddr = 0;
    testcase( pTerm->wtFlags & TERM_VIRTUAL );
    testcase( pTerm->wtFlags & TERM_CODED );
    if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
    if( (pTerm->prereqAll & pLevel->notReady)!=0 ){
      testcase( pWInfo->untestedTerms==0
               && (pWInfo->wctrlFlags & WHERE_ONETABLE_ONLY)!=0 );
      pWInfo->untestedTerms = 1;
      continue;
    }
    pE = pTerm->pExpr;
    assert( pE!=0 );
    if( pLevel->iLeftJoin && !ExprHasProperty(pE, EP_FromJoin) ){
      continue;
    }
    if( pTerm->wtFlags & TERM_LIKECOND ){
      assert( pLevel->iLikeRepCntr>0 );
      skipLikeAddr = sqlite3VdbeAddOp1(v, OP_IfNot, pLevel->iLikeRepCntr);
      VdbeCoverage(v);
    }
    sqlite3ExprIfFalse(pParse, pE, addrCont, SQLITE_JUMPIFNULL);
    if( skipLikeAddr ) sqlite3VdbeJumpHere(v, skipLikeAddr);
    pTerm->wtFlags |= TERM_CODED;
  }

  /* Insert code to test for implied constraints based on transitivity
  ** of the "==" operator.
  **
  ** Example: If the WHERE clause contains "t1.a=t2.b" and "t2.b=123"
  ** and we are coding the t1 loop and the t2 loop has not yet coded,
  ** then we cannot use the "t1.a=t2.b" constraint, but we can code
  ** the implied "t1.a=123" constraint.
  */
  for(pTerm=pWC->a, j=pWC->nTerm; j>0; j--, pTerm++){
    Expr *pE, *pEAlt;
    WhereTerm *pAlt;
    if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
    if( (pTerm->eOperator & (WO_EQ|WO_IS))==0 ) continue;
    if( (pTerm->eOperator & WO_EQUIV)==0 ) continue;
    if( pTerm->leftCursor!=iCur ) continue;
    if( pLevel->iLeftJoin ) continue;
    pE = pTerm->pExpr;
    assert( !ExprHasProperty(pE, EP_FromJoin) );
    assert( (pTerm->prereqRight & pLevel->notReady)!=0 );
    pAlt = findTerm(pWC, iCur, pTerm->u.leftColumn, notReady,
                    WO_EQ|WO_IN|WO_IS, 0);
    if( pAlt==0 ) continue;
    if( pAlt->wtFlags & (TERM_CODED) ) continue;
    testcase( pAlt->eOperator & WO_EQ );
    testcase( pAlt->eOperator & WO_IS );
    testcase( pAlt->eOperator & WO_IN );
    VdbeModuleComment((v, "begin transitive constraint"));
    pEAlt = sqlite3StackAllocRaw(db, sizeof(*pEAlt));
    if( pEAlt ){
      *pEAlt = *pAlt->pExpr;
      pEAlt->pLeft = pE->pLeft;
      sqlite3ExprIfFalse(pParse, pEAlt, addrCont, SQLITE_JUMPIFNULL);
      sqlite3StackFree(db, pEAlt);
    }
  }

  /* For a LEFT OUTER JOIN, generate code that will record the fact that
  ** at least one row of the right table has matched the left table.  
  */
  if( pLevel->iLeftJoin ){
    pLevel->addrFirst = sqlite3VdbeCurrentAddr(v);
    sqlite3VdbeAddOp2(v, OP_Integer, 1, pLevel->iLeftJoin);
    VdbeComment((v, "record LEFT JOIN hit"));
    sqlite3ExprCacheClear(pParse);
    for(pTerm=pWC->a, j=0; j<pWC->nTerm; j++, pTerm++){
      testcase( pTerm->wtFlags & TERM_VIRTUAL );
      testcase( pTerm->wtFlags & TERM_CODED );
      if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
      if( (pTerm->prereqAll & pLevel->notReady)!=0 ){
        assert( pWInfo->untestedTerms );
        continue;
      }
      assert( pTerm->pExpr );
      sqlite3ExprIfFalse(pParse, pTerm->pExpr, addrCont, SQLITE_JUMPIFNULL);
      pTerm->wtFlags |= TERM_CODED;
    }
  }

  return pLevel->notReady;
}

#ifdef WHERETRACE_ENABLED
/*
** Print the content of a WhereTerm object
*/
static void whereTermPrint(WhereTerm *pTerm, int iTerm){
  if( pTerm==0 ){







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2768
2769
2770
2771
2772
2773
2774









































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































2775
2776
2777
2778
2779
2780
2781
    WHERETRACE(0x10,("IN row estimate: est=%d\n", nRowEst));
  }
  assert( pBuilder->nRecValid==nRecValid );
  return rc;
}
#endif /* SQLITE_ENABLE_STAT3_OR_STAT4 */











































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































#ifdef WHERETRACE_ENABLED
/*
** Print the content of a WhereTerm object
*/
static void whereTermPrint(WhereTerm *pTerm, int iTerm){
  if( pTerm==0 ){
5666
5667
5668
5669
5670
5671
5672
5673
5674
5675
5676
5677
5678
5679
5680
  WhereLoop *pNew;

  /* Loop over the tables in the join, from left to right */
  pNew = pBuilder->pNew;
  whereLoopInit(pNew);
  for(iTab=0, pItem=pTabList->a; iTab<nTabList; iTab++, pItem++){
    pNew->iTab = iTab;
    pNew->maskSelf = getMask(&pWInfo->sMaskSet, pItem->iCursor);
    if( ((pItem->jointype|priorJoinType) & (JT_LEFT|JT_CROSS))!=0 ){
      mExtra = mPrior;
    }
    priorJoinType = pItem->jointype;
    if( IsVirtual(pItem->pTab) ){
      rc = whereLoopAddVirtual(pBuilder, mExtra);
    }else{







|







4194
4195
4196
4197
4198
4199
4200
4201
4202
4203
4204
4205
4206
4207
4208
  WhereLoop *pNew;

  /* Loop over the tables in the join, from left to right */
  pNew = pBuilder->pNew;
  whereLoopInit(pNew);
  for(iTab=0, pItem=pTabList->a; iTab<nTabList; iTab++, pItem++){
    pNew->iTab = iTab;
    pNew->maskSelf = sqlite3WhereGetMask(&pWInfo->sMaskSet, pItem->iCursor);
    if( ((pItem->jointype|priorJoinType) & (JT_LEFT|JT_CROSS))!=0 ){
      mExtra = mPrior;
    }
    priorJoinType = pItem->jointype;
    if( IsVirtual(pItem->pTab) ){
      rc = whereLoopAddVirtual(pBuilder, mExtra);
    }else{
5787
5788
5789
5790
5791
5792
5793
5794
5795
5796
5797
5798
5799
5800
5801
    ** loops.
    */
    for(i=0; i<nOrderBy; i++){
      if( MASKBIT(i) & obSat ) continue;
      pOBExpr = sqlite3ExprSkipCollate(pOrderBy->a[i].pExpr);
      if( pOBExpr->op!=TK_COLUMN ) continue;
      if( pOBExpr->iTable!=iCur ) continue;
      pTerm = findTerm(&pWInfo->sWC, iCur, pOBExpr->iColumn,
                       ~ready, WO_EQ|WO_ISNULL|WO_IS, 0);
      if( pTerm==0 ) continue;
      if( (pTerm->eOperator&(WO_EQ|WO_IS))!=0 && pOBExpr->iColumn>=0 ){
        const char *z1, *z2;
        pColl = sqlite3ExprCollSeq(pWInfo->pParse, pOrderBy->a[i].pExpr);
        if( !pColl ) pColl = db->pDfltColl;
        z1 = pColl->zName;







|







4315
4316
4317
4318
4319
4320
4321
4322
4323
4324
4325
4326
4327
4328
4329
    ** loops.
    */
    for(i=0; i<nOrderBy; i++){
      if( MASKBIT(i) & obSat ) continue;
      pOBExpr = sqlite3ExprSkipCollate(pOrderBy->a[i].pExpr);
      if( pOBExpr->op!=TK_COLUMN ) continue;
      if( pOBExpr->iTable!=iCur ) continue;
      pTerm = sqlite3WhereFindTerm(&pWInfo->sWC, iCur, pOBExpr->iColumn,
                       ~ready, WO_EQ|WO_ISNULL|WO_IS, 0);
      if( pTerm==0 ) continue;
      if( (pTerm->eOperator&(WO_EQ|WO_IS))!=0 && pOBExpr->iColumn>=0 ){
        const char *z1, *z2;
        pColl = sqlite3ExprCollSeq(pWInfo->pParse, pOrderBy->a[i].pExpr);
        if( !pColl ) pColl = db->pDfltColl;
        z1 = pColl->zName;
6403
6404
6405
6406
6407
6408
6409
6410
6411
6412
6413
6414
6415
6416
6417
6418
6419
6420
6421
6422
6423
6424
6425
6426
6427
6428
6429
6430
6431
6432
6433
6434
6435
6436
6437
6438
6439
6440
6441
6442
6443
6444
6445
6446
6447
6448
6449
6450
6451
6452
6453
6454
6455
6456
6457
  if( IsVirtual(pTab) ) return 0;
  if( pItem->zIndexedBy ) return 0;
  iCur = pItem->iCursor;
  pWC = &pWInfo->sWC;
  pLoop = pBuilder->pNew;
  pLoop->wsFlags = 0;
  pLoop->nSkip = 0;
  pTerm = findTerm(pWC, iCur, -1, 0, WO_EQ|WO_IS, 0);
  if( pTerm ){
    testcase( pTerm->eOperator & WO_IS );
    pLoop->wsFlags = WHERE_COLUMN_EQ|WHERE_IPK|WHERE_ONEROW;
    pLoop->aLTerm[0] = pTerm;
    pLoop->nLTerm = 1;
    pLoop->u.btree.nEq = 1;
    /* TUNING: Cost of a rowid lookup is 10 */
    pLoop->rRun = 33;  /* 33==sqlite3LogEst(10) */
  }else{
    for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
      int opMask;
      assert( pLoop->aLTermSpace==pLoop->aLTerm );
      if( !IsUniqueIndex(pIdx)
       || pIdx->pPartIdxWhere!=0 
       || pIdx->nKeyCol>ArraySize(pLoop->aLTermSpace) 
      ) continue;
      opMask = pIdx->uniqNotNull ? (WO_EQ|WO_IS) : WO_EQ;
      for(j=0; j<pIdx->nKeyCol; j++){
        pTerm = findTerm(pWC, iCur, pIdx->aiColumn[j], 0, opMask, pIdx);
        if( pTerm==0 ) break;
        testcase( pTerm->eOperator & WO_IS );
        pLoop->aLTerm[j] = pTerm;
      }
      if( j!=pIdx->nKeyCol ) continue;
      pLoop->wsFlags = WHERE_COLUMN_EQ|WHERE_ONEROW|WHERE_INDEXED;
      if( pIdx->isCovering || (pItem->colUsed & ~columnsInIndex(pIdx))==0 ){
        pLoop->wsFlags |= WHERE_IDX_ONLY;
      }
      pLoop->nLTerm = j;
      pLoop->u.btree.nEq = j;
      pLoop->u.btree.pIndex = pIdx;
      /* TUNING: Cost of a unique index lookup is 15 */
      pLoop->rRun = 39;  /* 39==sqlite3LogEst(15) */
      break;
    }
  }
  if( pLoop->wsFlags ){
    pLoop->nOut = (LogEst)1;
    pWInfo->a[0].pWLoop = pLoop;
    pLoop->maskSelf = getMask(&pWInfo->sMaskSet, iCur);
    pWInfo->a[0].iTabCur = iCur;
    pWInfo->nRowOut = 1;
    if( pWInfo->pOrderBy ) pWInfo->nOBSat =  pWInfo->pOrderBy->nExpr;
    if( pWInfo->wctrlFlags & WHERE_WANT_DISTINCT ){
      pWInfo->eDistinct = WHERE_DISTINCT_UNIQUE;
    }
#ifdef SQLITE_DEBUG







|


















|




















|







4931
4932
4933
4934
4935
4936
4937
4938
4939
4940
4941
4942
4943
4944
4945
4946
4947
4948
4949
4950
4951
4952
4953
4954
4955
4956
4957
4958
4959
4960
4961
4962
4963
4964
4965
4966
4967
4968
4969
4970
4971
4972
4973
4974
4975
4976
4977
4978
4979
4980
4981
4982
4983
4984
4985
  if( IsVirtual(pTab) ) return 0;
  if( pItem->zIndexedBy ) return 0;
  iCur = pItem->iCursor;
  pWC = &pWInfo->sWC;
  pLoop = pBuilder->pNew;
  pLoop->wsFlags = 0;
  pLoop->nSkip = 0;
  pTerm = sqlite3WhereFindTerm(pWC, iCur, -1, 0, WO_EQ|WO_IS, 0);
  if( pTerm ){
    testcase( pTerm->eOperator & WO_IS );
    pLoop->wsFlags = WHERE_COLUMN_EQ|WHERE_IPK|WHERE_ONEROW;
    pLoop->aLTerm[0] = pTerm;
    pLoop->nLTerm = 1;
    pLoop->u.btree.nEq = 1;
    /* TUNING: Cost of a rowid lookup is 10 */
    pLoop->rRun = 33;  /* 33==sqlite3LogEst(10) */
  }else{
    for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
      int opMask;
      assert( pLoop->aLTermSpace==pLoop->aLTerm );
      if( !IsUniqueIndex(pIdx)
       || pIdx->pPartIdxWhere!=0 
       || pIdx->nKeyCol>ArraySize(pLoop->aLTermSpace) 
      ) continue;
      opMask = pIdx->uniqNotNull ? (WO_EQ|WO_IS) : WO_EQ;
      for(j=0; j<pIdx->nKeyCol; j++){
        pTerm = sqlite3WhereFindTerm(pWC, iCur, pIdx->aiColumn[j], 0, opMask, pIdx);
        if( pTerm==0 ) break;
        testcase( pTerm->eOperator & WO_IS );
        pLoop->aLTerm[j] = pTerm;
      }
      if( j!=pIdx->nKeyCol ) continue;
      pLoop->wsFlags = WHERE_COLUMN_EQ|WHERE_ONEROW|WHERE_INDEXED;
      if( pIdx->isCovering || (pItem->colUsed & ~columnsInIndex(pIdx))==0 ){
        pLoop->wsFlags |= WHERE_IDX_ONLY;
      }
      pLoop->nLTerm = j;
      pLoop->u.btree.nEq = j;
      pLoop->u.btree.pIndex = pIdx;
      /* TUNING: Cost of a unique index lookup is 15 */
      pLoop->rRun = 39;  /* 39==sqlite3LogEst(15) */
      break;
    }
  }
  if( pLoop->wsFlags ){
    pLoop->nOut = (LogEst)1;
    pWInfo->a[0].pWLoop = pLoop;
    pLoop->maskSelf = sqlite3WhereGetMask(&pWInfo->sMaskSet, iCur);
    pWInfo->a[0].iTabCur = iCur;
    pWInfo->nRowOut = 1;
    if( pWInfo->pOrderBy ) pWInfo->nOBSat =  pWInfo->pOrderBy->nExpr;
    if( pWInfo->wctrlFlags & WHERE_WANT_DISTINCT ){
      pWInfo->eDistinct = WHERE_DISTINCT_UNIQUE;
    }
#ifdef SQLITE_DEBUG
6683
6684
6685
6686
6687
6688
6689
6690
6691
6692
6693
6694
6695
6696
6697
  for(ii=0; ii<pTabList->nSrc; ii++){
    createMask(pMaskSet, pTabList->a[ii].iCursor);
  }
#ifndef NDEBUG
  {
    Bitmask toTheLeft = 0;
    for(ii=0; ii<pTabList->nSrc; ii++){
      Bitmask m = getMask(pMaskSet, pTabList->a[ii].iCursor);
      assert( (m-1)==toTheLeft );
      toTheLeft |= m;
    }
  }
#endif

  /* Analyze all of the subexpressions. */







|







5211
5212
5213
5214
5215
5216
5217
5218
5219
5220
5221
5222
5223
5224
5225
  for(ii=0; ii<pTabList->nSrc; ii++){
    createMask(pMaskSet, pTabList->a[ii].iCursor);
  }
#ifndef NDEBUG
  {
    Bitmask toTheLeft = 0;
    for(ii=0; ii<pTabList->nSrc; ii++){
      Bitmask m = sqlite3WhereGetMask(pMaskSet, pTabList->a[ii].iCursor);
      assert( (m-1)==toTheLeft );
      toTheLeft |= m;
    }
  }
#endif

  /* Analyze all of the subexpressions. */
6932
6933
6934
6935
6936
6937
6938
6939
6940
6941
6942
6943
6944
6945
6946
6947
6948
6949
6950
6951
6952
6953
#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
    if( (pLevel->pWLoop->wsFlags & WHERE_AUTO_INDEX)!=0 ){
      constructAutomaticIndex(pParse, &pWInfo->sWC,
                &pTabList->a[pLevel->iFrom], notReady, pLevel);
      if( db->mallocFailed ) goto whereBeginError;
    }
#endif
    addrExplain = explainOneScan(
        pParse, pTabList, pLevel, ii, pLevel->iFrom, wctrlFlags
    );
    pLevel->addrBody = sqlite3VdbeCurrentAddr(v);
    notReady = codeOneLoopStart(pWInfo, ii, notReady);
    pWInfo->iContinue = pLevel->addrCont;
    if( (wsFlags&WHERE_MULTI_OR)==0 && (wctrlFlags&WHERE_ONETABLE_ONLY)==0 ){
      addScanStatus(v, pTabList, pLevel, addrExplain);
    }
  }

  /* Done. */
  VdbeModuleComment((v, "Begin WHERE-core"));
  return pWInfo;








|



|


|







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#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
    if( (pLevel->pWLoop->wsFlags & WHERE_AUTO_INDEX)!=0 ){
      constructAutomaticIndex(pParse, &pWInfo->sWC,
                &pTabList->a[pLevel->iFrom], notReady, pLevel);
      if( db->mallocFailed ) goto whereBeginError;
    }
#endif
    addrExplain = sqlite3WhereExplainOneScan(
        pParse, pTabList, pLevel, ii, pLevel->iFrom, wctrlFlags
    );
    pLevel->addrBody = sqlite3VdbeCurrentAddr(v);
    notReady = sqlite3WhereCodeOneLoopStart(pWInfo, ii, notReady);
    pWInfo->iContinue = pLevel->addrCont;
    if( (wsFlags&WHERE_MULTI_OR)==0 && (wctrlFlags&WHERE_ONETABLE_ONLY)==0 ){
      sqlite3WhereAddScanStatus(v, pTabList, pLevel, addrExplain);
    }
  }

  /* Done. */
  VdbeModuleComment((v, "Begin WHERE-core"));
  return pWInfo;

Changes to src/whereInt.h.
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** a separate source file for easier editing.
*/

/*
** Trace output macros
*/
#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
/***/ int sqlite3WhereTrace = 0;
#endif
#if defined(SQLITE_DEBUG) \
    && (defined(SQLITE_TEST) || defined(SQLITE_ENABLE_WHERETRACE))
# define WHERETRACE(K,X)  if(sqlite3WhereTrace&(K)) sqlite3DebugPrintf X
# define WHERETRACE_ENABLED 1
#else
# define WHERETRACE(K,X)







|







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** a separate source file for easier editing.
*/

/*
** Trace output macros
*/
#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
/***/ int sqlite3WhereTrace;
#endif
#if defined(SQLITE_DEBUG) \
    && (defined(SQLITE_TEST) || defined(SQLITE_ENABLE_WHERETRACE))
# define WHERETRACE(K,X)  if(sqlite3WhereTrace&(K)) sqlite3DebugPrintf X
# define WHERETRACE_ENABLED 1
#else
# define WHERETRACE(K,X)
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*/
#define N_OR_COST 3
struct WhereOrSet {
  u16 n;                      /* Number of valid a[] entries */
  WhereOrCost a[N_OR_COST];   /* Set of best costs */
};


/* Forward declaration of methods */
static int whereLoopResize(sqlite3*, WhereLoop*, int);

/*
** Each instance of this object holds a sequence of WhereLoop objects
** that implement some or all of a query plan.
**
** Think of each WhereLoop object as a node in a graph with arcs
** showing dependencies and costs for travelling between nodes.  (That is
** not a completely accurate description because WhereLoop costs are a







<
<
<
<







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170
*/
#define N_OR_COST 3
struct WhereOrSet {
  u16 n;                      /* Number of valid a[] entries */
  WhereOrCost a[N_OR_COST];   /* Set of best costs */
};





/*
** Each instance of this object holds a sequence of WhereLoop objects
** that implement some or all of a query plan.
**
** Think of each WhereLoop object as a node in a graph with arcs
** showing dependencies and costs for travelling between nodes.  (That is
** not a completely accurate description because WhereLoop costs are a
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420
421
422
423
424














































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431
  int iBreak;               /* Jump here to break out of the loop */
  int savedNQueryLoop;      /* pParse->nQueryLoop outside the WHERE loop */
  int aiCurOnePass[2];      /* OP_OpenWrite cursors for the ONEPASS opt */
  WhereMaskSet sMaskSet;    /* Map cursor numbers to bitmasks */
  WhereClause sWC;          /* Decomposition of the WHERE clause */
  WhereLevel a[1];          /* Information about each nest loop in WHERE */
};















































/*
** Bitmasks for the operators on WhereTerm objects.  These are all
** operators that are of interest to the query planner.  An
** OR-ed combination of these values can be used when searching for
** particular WhereTerms within a WhereClause.
*/







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  int iBreak;               /* Jump here to break out of the loop */
  int savedNQueryLoop;      /* pParse->nQueryLoop outside the WHERE loop */
  int aiCurOnePass[2];      /* OP_OpenWrite cursors for the ONEPASS opt */
  WhereMaskSet sMaskSet;    /* Map cursor numbers to bitmasks */
  WhereClause sWC;          /* Decomposition of the WHERE clause */
  WhereLevel a[1];          /* Information about each nest loop in WHERE */
};

/*
** Private interfaces - callable only by other where.c routines.
*/
Bitmask sqlite3WhereGetMask(WhereMaskSet*,int);
WhereTerm *sqlite3WhereFindTerm(
  WhereClause *pWC,     /* The WHERE clause to be searched */
  int iCur,             /* Cursor number of LHS */
  int iColumn,          /* Column number of LHS */
  Bitmask notReady,     /* RHS must not overlap with this mask */
  u32 op,               /* Mask of WO_xx values describing operator */
  Index *pIdx           /* Must be compatible with this index, if not NULL */
);
#ifndef SQLITE_OMIT_EXPLAIN
int sqlite3WhereExplainOneScan(
  Parse *pParse,                  /* Parse context */
  SrcList *pTabList,              /* Table list this loop refers to */
  WhereLevel *pLevel,             /* Scan to write OP_Explain opcode for */
  int iLevel,                     /* Value for "level" column of output */
  int iFrom,                      /* Value for "from" column of output */
  u16 wctrlFlags                  /* Flags passed to sqlite3WhereBegin() */
);
#else
# define sqlite3WhereExplainOneScan(u,v,w,x,y,z) 0
#endif /* SQLITE_OMIT_EXPLAIN */
#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
void sqlite3WhereAddScanStatus(
  Vdbe *v,                        /* Vdbe to add scanstatus entry to */
  SrcList *pSrclist,              /* FROM clause pLvl reads data from */
  WhereLevel *pLvl,               /* Level to add scanstatus() entry for */
  int addrExplain                 /* Address of OP_Explain (or 0) */
);
#else
# define sqlite3WhereAddScanStatus(a, b, c, d) ((void)d)
#endif
Bitmask sqlite3WhereCodeOneLoopStart(
  WhereInfo *pWInfo,   /* Complete information about the WHERE clause */
  int iLevel,          /* Which level of pWInfo->a[] should be coded */
  Bitmask notReady     /* Which tables are currently available */
);







/*
** Bitmasks for the operators on WhereTerm objects.  These are all
** operators that are of interest to the query planner.  An
** OR-ed combination of these values can be used when searching for
** particular WhereTerms within a WhereClause.
*/
Added src/wherecode.c.


























































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































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/*
** 2015-06-06
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This module contains C code that generates VDBE code used to process
** the WHERE clause of SQL statements.
**
** This file was split off from where.c on 2015-06-06 in order to reduce the
** size of where.c and make it easier to edit.  This file contains the routines
** that actually generate the bulk of the WHERE loop code.  The original where.c
** file retains the code that does query planning and analysis.
*/
#include "sqliteInt.h"
#include "whereInt.h"

#ifndef SQLITE_OMIT_EXPLAIN
/*
** This routine is a helper for explainIndexRange() below
**
** pStr holds the text of an expression that we are building up one term
** at a time.  This routine adds a new term to the end of the expression.
** Terms are separated by AND so add the "AND" text for second and subsequent
** terms only.
*/
static void explainAppendTerm(
  StrAccum *pStr,             /* The text expression being built */
  int iTerm,                  /* Index of this term.  First is zero */
  const char *zColumn,        /* Name of the column */
  const char *zOp             /* Name of the operator */
){
  if( iTerm ) sqlite3StrAccumAppend(pStr, " AND ", 5);
  sqlite3StrAccumAppendAll(pStr, zColumn);
  sqlite3StrAccumAppend(pStr, zOp, 1);
  sqlite3StrAccumAppend(pStr, "?", 1);
}

/*
** Argument pLevel describes a strategy for scanning table pTab. This 
** function appends text to pStr that describes the subset of table
** rows scanned by the strategy in the form of an SQL expression.
**
** For example, if the query:
**
**   SELECT * FROM t1 WHERE a=1 AND b>2;
**
** is run and there is an index on (a, b), then this function returns a
** string similar to:
**
**   "a=? AND b>?"
*/
static void explainIndexRange(StrAccum *pStr, WhereLoop *pLoop, Table *pTab){
  Index *pIndex = pLoop->u.btree.pIndex;
  u16 nEq = pLoop->u.btree.nEq;
  u16 nSkip = pLoop->nSkip;
  int i, j;
  Column *aCol = pTab->aCol;
  i16 *aiColumn = pIndex->aiColumn;

  if( nEq==0 && (pLoop->wsFlags&(WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))==0 ) return;
  sqlite3StrAccumAppend(pStr, " (", 2);
  for(i=0; i<nEq; i++){
    char *z = aiColumn[i] < 0 ? "rowid" : aCol[aiColumn[i]].zName;
    if( i>=nSkip ){
      explainAppendTerm(pStr, i, z, "=");
    }else{
      if( i ) sqlite3StrAccumAppend(pStr, " AND ", 5);
      sqlite3XPrintf(pStr, 0, "ANY(%s)", z);
    }
  }

  j = i;
  if( pLoop->wsFlags&WHERE_BTM_LIMIT ){
    char *z = aiColumn[j] < 0 ? "rowid" : aCol[aiColumn[j]].zName;
    explainAppendTerm(pStr, i++, z, ">");
  }
  if( pLoop->wsFlags&WHERE_TOP_LIMIT ){
    char *z = aiColumn[j] < 0 ? "rowid" : aCol[aiColumn[j]].zName;
    explainAppendTerm(pStr, i, z, "<");
  }
  sqlite3StrAccumAppend(pStr, ")", 1);
}

/*
** This function is a no-op unless currently processing an EXPLAIN QUERY PLAN
** command, or if either SQLITE_DEBUG or SQLITE_ENABLE_STMT_SCANSTATUS was
** defined at compile-time. If it is not a no-op, a single OP_Explain opcode 
** is added to the output to describe the table scan strategy in pLevel.
**
** If an OP_Explain opcode is added to the VM, its address is returned.
** Otherwise, if no OP_Explain is coded, zero is returned.
*/
int sqlite3WhereExplainOneScan(
  Parse *pParse,                  /* Parse context */
  SrcList *pTabList,              /* Table list this loop refers to */
  WhereLevel *pLevel,             /* Scan to write OP_Explain opcode for */
  int iLevel,                     /* Value for "level" column of output */
  int iFrom,                      /* Value for "from" column of output */
  u16 wctrlFlags                  /* Flags passed to sqlite3WhereBegin() */
){
  int ret = 0;
#if !defined(SQLITE_DEBUG) && !defined(SQLITE_ENABLE_STMT_SCANSTATUS)
  if( pParse->explain==2 )
#endif
  {
    struct SrcList_item *pItem = &pTabList->a[pLevel->iFrom];
    Vdbe *v = pParse->pVdbe;      /* VM being constructed */
    sqlite3 *db = pParse->db;     /* Database handle */
    int iId = pParse->iSelectId;  /* Select id (left-most output column) */
    int isSearch;                 /* True for a SEARCH. False for SCAN. */
    WhereLoop *pLoop;             /* The controlling WhereLoop object */
    u32 flags;                    /* Flags that describe this loop */
    char *zMsg;                   /* Text to add to EQP output */
    StrAccum str;                 /* EQP output string */
    char zBuf[100];               /* Initial space for EQP output string */

    pLoop = pLevel->pWLoop;
    flags = pLoop->wsFlags;
    if( (flags&WHERE_MULTI_OR) || (wctrlFlags&WHERE_ONETABLE_ONLY) ) return 0;

    isSearch = (flags&(WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))!=0
            || ((flags&WHERE_VIRTUALTABLE)==0 && (pLoop->u.btree.nEq>0))
            || (wctrlFlags&(WHERE_ORDERBY_MIN|WHERE_ORDERBY_MAX));

    sqlite3StrAccumInit(&str, db, zBuf, sizeof(zBuf), SQLITE_MAX_LENGTH);
    sqlite3StrAccumAppendAll(&str, isSearch ? "SEARCH" : "SCAN");
    if( pItem->pSelect ){
      sqlite3XPrintf(&str, 0, " SUBQUERY %d", pItem->iSelectId);
    }else{
      sqlite3XPrintf(&str, 0, " TABLE %s", pItem->zName);
    }

    if( pItem->zAlias ){
      sqlite3XPrintf(&str, 0, " AS %s", pItem->zAlias);
    }
    if( (flags & (WHERE_IPK|WHERE_VIRTUALTABLE))==0 ){
      const char *zFmt = 0;
      Index *pIdx;

      assert( pLoop->u.btree.pIndex!=0 );
      pIdx = pLoop->u.btree.pIndex;
      assert( !(flags&WHERE_AUTO_INDEX) || (flags&WHERE_IDX_ONLY) );
      if( !HasRowid(pItem->pTab) && IsPrimaryKeyIndex(pIdx) ){
        if( isSearch ){
          zFmt = "PRIMARY KEY";
        }
      }else if( flags & WHERE_PARTIALIDX ){
        zFmt = "AUTOMATIC PARTIAL COVERING INDEX";
      }else if( flags & WHERE_AUTO_INDEX ){
        zFmt = "AUTOMATIC COVERING INDEX";
      }else if( flags & WHERE_IDX_ONLY ){
        zFmt = "COVERING INDEX %s";
      }else{
        zFmt = "INDEX %s";
      }
      if( zFmt ){
        sqlite3StrAccumAppend(&str, " USING ", 7);
        sqlite3XPrintf(&str, 0, zFmt, pIdx->zName);
        explainIndexRange(&str, pLoop, pItem->pTab);
      }
    }else if( (flags & WHERE_IPK)!=0 && (flags & WHERE_CONSTRAINT)!=0 ){
      const char *zRange;
      if( flags&(WHERE_COLUMN_EQ|WHERE_COLUMN_IN) ){
        zRange = "(rowid=?)";
      }else if( (flags&WHERE_BOTH_LIMIT)==WHERE_BOTH_LIMIT ){
        zRange = "(rowid>? AND rowid<?)";
      }else if( flags&WHERE_BTM_LIMIT ){
        zRange = "(rowid>?)";
      }else{
        assert( flags&WHERE_TOP_LIMIT);
        zRange = "(rowid<?)";
      }
      sqlite3StrAccumAppendAll(&str, " USING INTEGER PRIMARY KEY ");
      sqlite3StrAccumAppendAll(&str, zRange);
    }
#ifndef SQLITE_OMIT_VIRTUALTABLE
    else if( (flags & WHERE_VIRTUALTABLE)!=0 ){
      sqlite3XPrintf(&str, 0, " VIRTUAL TABLE INDEX %d:%s",
                  pLoop->u.vtab.idxNum, pLoop->u.vtab.idxStr);
    }
#endif
#ifdef SQLITE_EXPLAIN_ESTIMATED_ROWS
    if( pLoop->nOut>=10 ){
      sqlite3XPrintf(&str, 0, " (~%llu rows)", sqlite3LogEstToInt(pLoop->nOut));
    }else{
      sqlite3StrAccumAppend(&str, " (~1 row)", 9);
    }
#endif
    zMsg = sqlite3StrAccumFinish(&str);
    ret = sqlite3VdbeAddOp4(v, OP_Explain, iId, iLevel, iFrom, zMsg,P4_DYNAMIC);
  }
  return ret;
}
#endif /* SQLITE_OMIT_EXPLAIN */

#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
/*
** Configure the VM passed as the first argument with an
** sqlite3_stmt_scanstatus() entry corresponding to the scan used to 
** implement level pLvl. Argument pSrclist is a pointer to the FROM 
** clause that the scan reads data from.
**
** If argument addrExplain is not 0, it must be the address of an 
** OP_Explain instruction that describes the same loop.
*/
void sqlite3WhereAddScanStatus(
  Vdbe *v,                        /* Vdbe to add scanstatus entry to */
  SrcList *pSrclist,              /* FROM clause pLvl reads data from */
  WhereLevel *pLvl,               /* Level to add scanstatus() entry for */
  int addrExplain                 /* Address of OP_Explain (or 0) */
){
  const char *zObj = 0;
  WhereLoop *pLoop = pLvl->pWLoop;
  if( (pLoop->wsFlags & WHERE_VIRTUALTABLE)==0  &&  pLoop->u.btree.pIndex!=0 ){
    zObj = pLoop->u.btree.pIndex->zName;
  }else{
    zObj = pSrclist->a[pLvl->iFrom].zName;
  }
  sqlite3VdbeScanStatus(
      v, addrExplain, pLvl->addrBody, pLvl->addrVisit, pLoop->nOut, zObj
  );
}
#endif


/*
** Disable a term in the WHERE clause.  Except, do not disable the term
** if it controls a LEFT OUTER JOIN and it did not originate in the ON
** or USING clause of that join.
**
** Consider the term t2.z='ok' in the following queries:
**
**   (1)  SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x WHERE t2.z='ok'
**   (2)  SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x AND t2.z='ok'
**   (3)  SELECT * FROM t1, t2 WHERE t1.a=t2.x AND t2.z='ok'
**
** The t2.z='ok' is disabled in the in (2) because it originates
** in the ON clause.  The term is disabled in (3) because it is not part
** of a LEFT OUTER JOIN.  In (1), the term is not disabled.
**
** Disabling a term causes that term to not be tested in the inner loop
** of the join.  Disabling is an optimization.  When terms are satisfied
** by indices, we disable them to prevent redundant tests in the inner
** loop.  We would get the correct results if nothing were ever disabled,
** but joins might run a little slower.  The trick is to disable as much
** as we can without disabling too much.  If we disabled in (1), we'd get
** the wrong answer.  See ticket #813.
**
** If all the children of a term are disabled, then that term is also
** automatically disabled.  In this way, terms get disabled if derived
** virtual terms are tested first.  For example:
**
**      x GLOB 'abc*' AND x>='abc' AND x<'acd'
**      \___________/     \______/     \_____/
**         parent          child1       child2
**
** Only the parent term was in the original WHERE clause.  The child1
** and child2 terms were added by the LIKE optimization.  If both of
** the virtual child terms are valid, then testing of the parent can be 
** skipped.
**
** Usually the parent term is marked as TERM_CODED.  But if the parent
** term was originally TERM_LIKE, then the parent gets TERM_LIKECOND instead.
** The TERM_LIKECOND marking indicates that the term should be coded inside
** a conditional such that is only evaluated on the second pass of a
** LIKE-optimization loop, when scanning BLOBs instead of strings.
*/
static void disableTerm(WhereLevel *pLevel, WhereTerm *pTerm){
  int nLoop = 0;
  while( pTerm
      && (pTerm->wtFlags & TERM_CODED)==0
      && (pLevel->iLeftJoin==0 || ExprHasProperty(pTerm->pExpr, EP_FromJoin))
      && (pLevel->notReady & pTerm->prereqAll)==0
  ){
    if( nLoop && (pTerm->wtFlags & TERM_LIKE)!=0 ){
      pTerm->wtFlags |= TERM_LIKECOND;
    }else{
      pTerm->wtFlags |= TERM_CODED;
    }
    if( pTerm->iParent<0 ) break;
    pTerm = &pTerm->pWC->a[pTerm->iParent];
    pTerm->nChild--;
    if( pTerm->nChild!=0 ) break;
    nLoop++;
  }
}

/*
** Code an OP_Affinity opcode to apply the column affinity string zAff
** to the n registers starting at base. 
**
** As an optimization, SQLITE_AFF_BLOB entries (which are no-ops) at the
** beginning and end of zAff are ignored.  If all entries in zAff are
** SQLITE_AFF_BLOB, then no code gets generated.
**
** This routine makes its own copy of zAff so that the caller is free
** to modify zAff after this routine returns.
*/
static void codeApplyAffinity(Parse *pParse, int base, int n, char *zAff){
  Vdbe *v = pParse->pVdbe;
  if( zAff==0 ){
    assert( pParse->db->mallocFailed );
    return;
  }
  assert( v!=0 );

  /* Adjust base and n to skip over SQLITE_AFF_BLOB entries at the beginning
  ** and end of the affinity string.
  */
  while( n>0 && zAff[0]==SQLITE_AFF_BLOB ){
    n--;
    base++;
    zAff++;
  }
  while( n>1 && zAff[n-1]==SQLITE_AFF_BLOB ){
    n--;
  }

  /* Code the OP_Affinity opcode if there is anything left to do. */
  if( n>0 ){
    sqlite3VdbeAddOp2(v, OP_Affinity, base, n);
    sqlite3VdbeChangeP4(v, -1, zAff, n);
    sqlite3ExprCacheAffinityChange(pParse, base, n);
  }
}


/*
** Generate code for a single equality term of the WHERE clause.  An equality
** term can be either X=expr or X IN (...).   pTerm is the term to be 
** coded.
**
** The current value for the constraint is left in register iReg.
**
** For a constraint of the form X=expr, the expression is evaluated and its
** result is left on the stack.  For constraints of the form X IN (...)
** this routine sets up a loop that will iterate over all values of X.
*/
static int codeEqualityTerm(
  Parse *pParse,      /* The parsing context */
  WhereTerm *pTerm,   /* The term of the WHERE clause to be coded */
  WhereLevel *pLevel, /* The level of the FROM clause we are working on */
  int iEq,            /* Index of the equality term within this level */
  int bRev,           /* True for reverse-order IN operations */
  int iTarget         /* Attempt to leave results in this register */
){
  Expr *pX = pTerm->pExpr;
  Vdbe *v = pParse->pVdbe;
  int iReg;                  /* Register holding results */

  assert( iTarget>0 );
  if( pX->op==TK_EQ || pX->op==TK_IS ){
    iReg = sqlite3ExprCodeTarget(pParse, pX->pRight, iTarget);
  }else if( pX->op==TK_ISNULL ){
    iReg = iTarget;
    sqlite3VdbeAddOp2(v, OP_Null, 0, iReg);
#ifndef SQLITE_OMIT_SUBQUERY
  }else{
    int eType;
    int iTab;
    struct InLoop *pIn;
    WhereLoop *pLoop = pLevel->pWLoop;

    if( (pLoop->wsFlags & WHERE_VIRTUALTABLE)==0
      && pLoop->u.btree.pIndex!=0
      && pLoop->u.btree.pIndex->aSortOrder[iEq]
    ){
      testcase( iEq==0 );
      testcase( bRev );
      bRev = !bRev;
    }
    assert( pX->op==TK_IN );
    iReg = iTarget;
    eType = sqlite3FindInIndex(pParse, pX, IN_INDEX_LOOP, 0);
    if( eType==IN_INDEX_INDEX_DESC ){
      testcase( bRev );
      bRev = !bRev;
    }
    iTab = pX->iTable;
    sqlite3VdbeAddOp2(v, bRev ? OP_Last : OP_Rewind, iTab, 0);
    VdbeCoverageIf(v, bRev);
    VdbeCoverageIf(v, !bRev);
    assert( (pLoop->wsFlags & WHERE_MULTI_OR)==0 );
    pLoop->wsFlags |= WHERE_IN_ABLE;
    if( pLevel->u.in.nIn==0 ){
      pLevel->addrNxt = sqlite3VdbeMakeLabel(v);
    }
    pLevel->u.in.nIn++;
    pLevel->u.in.aInLoop =
       sqlite3DbReallocOrFree(pParse->db, pLevel->u.in.aInLoop,
                              sizeof(pLevel->u.in.aInLoop[0])*pLevel->u.in.nIn);
    pIn = pLevel->u.in.aInLoop;
    if( pIn ){
      pIn += pLevel->u.in.nIn - 1;
      pIn->iCur = iTab;
      if( eType==IN_INDEX_ROWID ){
        pIn->addrInTop = sqlite3VdbeAddOp2(v, OP_Rowid, iTab, iReg);
      }else{
        pIn->addrInTop = sqlite3VdbeAddOp3(v, OP_Column, iTab, 0, iReg);
      }
      pIn->eEndLoopOp = bRev ? OP_PrevIfOpen : OP_NextIfOpen;
      sqlite3VdbeAddOp1(v, OP_IsNull, iReg); VdbeCoverage(v);
    }else{
      pLevel->u.in.nIn = 0;
    }
#endif
  }
  disableTerm(pLevel, pTerm);
  return iReg;
}

/*
** Generate code that will evaluate all == and IN constraints for an
** index scan.
**
** For example, consider table t1(a,b,c,d,e,f) with index i1(a,b,c).
** Suppose the WHERE clause is this:  a==5 AND b IN (1,2,3) AND c>5 AND c<10
** The index has as many as three equality constraints, but in this
** example, the third "c" value is an inequality.  So only two 
** constraints are coded.  This routine will generate code to evaluate
** a==5 and b IN (1,2,3).  The current values for a and b will be stored
** in consecutive registers and the index of the first register is returned.
**
** In the example above nEq==2.  But this subroutine works for any value
** of nEq including 0.  If nEq==0, this routine is nearly a no-op.
** The only thing it does is allocate the pLevel->iMem memory cell and
** compute the affinity string.
**
** The nExtraReg parameter is 0 or 1.  It is 0 if all WHERE clause constraints
** are == or IN and are covered by the nEq.  nExtraReg is 1 if there is
** an inequality constraint (such as the "c>=5 AND c<10" in the example) that
** occurs after the nEq quality constraints.
**
** This routine allocates a range of nEq+nExtraReg memory cells and returns
** the index of the first memory cell in that range. The code that
** calls this routine will use that memory range to store keys for
** start and termination conditions of the loop.
** key value of the loop.  If one or more IN operators appear, then
** this routine allocates an additional nEq memory cells for internal
** use.
**
** Before returning, *pzAff is set to point to a buffer containing a
** copy of the column affinity string of the index allocated using
** sqlite3DbMalloc(). Except, entries in the copy of the string associated
** with equality constraints that use BLOB or NONE affinity are set to
** SQLITE_AFF_BLOB. This is to deal with SQL such as the following:
**
**   CREATE TABLE t1(a TEXT PRIMARY KEY, b);
**   SELECT ... FROM t1 AS t2, t1 WHERE t1.a = t2.b;
**
** In the example above, the index on t1(a) has TEXT affinity. But since
** the right hand side of the equality constraint (t2.b) has BLOB/NONE affinity,
** no conversion should be attempted before using a t2.b value as part of
** a key to search the index. Hence the first byte in the returned affinity
** string in this example would be set to SQLITE_AFF_BLOB.
*/
static int codeAllEqualityTerms(
  Parse *pParse,        /* Parsing context */
  WhereLevel *pLevel,   /* Which nested loop of the FROM we are coding */
  int bRev,             /* Reverse the order of IN operators */
  int nExtraReg,        /* Number of extra registers to allocate */
  char **pzAff          /* OUT: Set to point to affinity string */
){
  u16 nEq;                      /* The number of == or IN constraints to code */
  u16 nSkip;                    /* Number of left-most columns to skip */
  Vdbe *v = pParse->pVdbe;      /* The vm under construction */
  Index *pIdx;                  /* The index being used for this loop */
  WhereTerm *pTerm;             /* A single constraint term */
  WhereLoop *pLoop;             /* The WhereLoop object */
  int j;                        /* Loop counter */
  int regBase;                  /* Base register */
  int nReg;                     /* Number of registers to allocate */
  char *zAff;                   /* Affinity string to return */

  /* This module is only called on query plans that use an index. */
  pLoop = pLevel->pWLoop;
  assert( (pLoop->wsFlags & WHERE_VIRTUALTABLE)==0 );
  nEq = pLoop->u.btree.nEq;
  nSkip = pLoop->nSkip;
  pIdx = pLoop->u.btree.pIndex;
  assert( pIdx!=0 );

  /* Figure out how many memory cells we will need then allocate them.
  */
  regBase = pParse->nMem + 1;
  nReg = pLoop->u.btree.nEq + nExtraReg;
  pParse->nMem += nReg;

  zAff = sqlite3DbStrDup(pParse->db, sqlite3IndexAffinityStr(v, pIdx));
  if( !zAff ){
    pParse->db->mallocFailed = 1;
  }

  if( nSkip ){
    int iIdxCur = pLevel->iIdxCur;
    sqlite3VdbeAddOp1(v, (bRev?OP_Last:OP_Rewind), iIdxCur);
    VdbeCoverageIf(v, bRev==0);
    VdbeCoverageIf(v, bRev!=0);
    VdbeComment((v, "begin skip-scan on %s", pIdx->zName));
    j = sqlite3VdbeAddOp0(v, OP_Goto);
    pLevel->addrSkip = sqlite3VdbeAddOp4Int(v, (bRev?OP_SeekLT:OP_SeekGT),
                            iIdxCur, 0, regBase, nSkip);
    VdbeCoverageIf(v, bRev==0);
    VdbeCoverageIf(v, bRev!=0);
    sqlite3VdbeJumpHere(v, j);
    for(j=0; j<nSkip; j++){
      sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, j, regBase+j);
      assert( pIdx->aiColumn[j]>=0 );
      VdbeComment((v, "%s", pIdx->pTable->aCol[pIdx->aiColumn[j]].zName));
    }
  }    

  /* Evaluate the equality constraints
  */
  assert( zAff==0 || (int)strlen(zAff)>=nEq );
  for(j=nSkip; j<nEq; j++){
    int r1;
    pTerm = pLoop->aLTerm[j];
    assert( pTerm!=0 );
    /* The following testcase is true for indices with redundant columns. 
    ** Ex: CREATE INDEX i1 ON t1(a,b,a); SELECT * FROM t1 WHERE a=0 AND b=0; */
    testcase( (pTerm->wtFlags & TERM_CODED)!=0 );
    testcase( pTerm->wtFlags & TERM_VIRTUAL );
    r1 = codeEqualityTerm(pParse, pTerm, pLevel, j, bRev, regBase+j);
    if( r1!=regBase+j ){
      if( nReg==1 ){
        sqlite3ReleaseTempReg(pParse, regBase);
        regBase = r1;
      }else{
        sqlite3VdbeAddOp2(v, OP_SCopy, r1, regBase+j);
      }
    }
    testcase( pTerm->eOperator & WO_ISNULL );
    testcase( pTerm->eOperator & WO_IN );
    if( (pTerm->eOperator & (WO_ISNULL|WO_IN))==0 ){
      Expr *pRight = pTerm->pExpr->pRight;
      if( (pTerm->wtFlags & TERM_IS)==0 && sqlite3ExprCanBeNull(pRight) ){
        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+j, pLevel->addrBrk);
        VdbeCoverage(v);
      }
      if( zAff ){
        if( sqlite3CompareAffinity(pRight, zAff[j])==SQLITE_AFF_BLOB ){
          zAff[j] = SQLITE_AFF_BLOB;
        }
        if( sqlite3ExprNeedsNoAffinityChange(pRight, zAff[j]) ){
          zAff[j] = SQLITE_AFF_BLOB;
        }
      }
    }
  }
  *pzAff = zAff;
  return regBase;
}

/*
** If the most recently coded instruction is a constant range contraint
** that originated from the LIKE optimization, then change the P3 to be
** pLoop->iLikeRepCntr and set P5.
**
** The LIKE optimization trys to evaluate "x LIKE 'abc%'" as a range
** expression: "x>='ABC' AND x<'abd'".  But this requires that the range
** scan loop run twice, once for strings and a second time for BLOBs.
** The OP_String opcodes on the second pass convert the upper and lower
** bound string contants to blobs.  This routine makes the necessary changes
** to the OP_String opcodes for that to happen.
*/
static void whereLikeOptimizationStringFixup(
  Vdbe *v,                /* prepared statement under construction */
  WhereLevel *pLevel,     /* The loop that contains the LIKE operator */
  WhereTerm *pTerm        /* The upper or lower bound just coded */
){
  if( pTerm->wtFlags & TERM_LIKEOPT ){
    VdbeOp *pOp;
    assert( pLevel->iLikeRepCntr>0 );
    pOp = sqlite3VdbeGetOp(v, -1);
    assert( pOp!=0 );
    assert( pOp->opcode==OP_String8 
            || pTerm->pWC->pWInfo->pParse->db->mallocFailed );
    pOp->p3 = pLevel->iLikeRepCntr;
    pOp->p5 = 1;
  }
}


/*
** Generate code for the start of the iLevel-th loop in the WHERE clause
** implementation described by pWInfo.
*/
Bitmask sqlite3WhereCodeOneLoopStart(
  WhereInfo *pWInfo,   /* Complete information about the WHERE clause */
  int iLevel,          /* Which level of pWInfo->a[] should be coded */
  Bitmask notReady     /* Which tables are currently available */
){
  int j, k;            /* Loop counters */
  int iCur;            /* The VDBE cursor for the table */
  int addrNxt;         /* Where to jump to continue with the next IN case */
  int omitTable;       /* True if we use the index only */
  int bRev;            /* True if we need to scan in reverse order */
  WhereLevel *pLevel;  /* The where level to be coded */
  WhereLoop *pLoop;    /* The WhereLoop object being coded */
  WhereClause *pWC;    /* Decomposition of the entire WHERE clause */
  WhereTerm *pTerm;               /* A WHERE clause term */
  Parse *pParse;                  /* Parsing context */
  sqlite3 *db;                    /* Database connection */
  Vdbe *v;                        /* The prepared stmt under constructions */
  struct SrcList_item *pTabItem;  /* FROM clause term being coded */
  int addrBrk;                    /* Jump here to break out of the loop */
  int addrCont;                   /* Jump here to continue with next cycle */
  int iRowidReg = 0;        /* Rowid is stored in this register, if not zero */
  int iReleaseReg = 0;      /* Temp register to free before returning */

  pParse = pWInfo->pParse;
  v = pParse->pVdbe;
  pWC = &pWInfo->sWC;
  db = pParse->db;
  pLevel = &pWInfo->a[iLevel];
  pLoop = pLevel->pWLoop;
  pTabItem = &pWInfo->pTabList->a[pLevel->iFrom];
  iCur = pTabItem->iCursor;
  pLevel->notReady = notReady & ~sqlite3WhereGetMask(&pWInfo->sMaskSet, iCur);
  bRev = (pWInfo->revMask>>iLevel)&1;
  omitTable = (pLoop->wsFlags & WHERE_IDX_ONLY)!=0 
           && (pWInfo->wctrlFlags & WHERE_FORCE_TABLE)==0;
  VdbeModuleComment((v, "Begin WHERE-loop%d: %s",iLevel,pTabItem->pTab->zName));

  /* Create labels for the "break" and "continue" instructions
  ** for the current loop.  Jump to addrBrk to break out of a loop.
  ** Jump to cont to go immediately to the next iteration of the
  ** loop.
  **
  ** When there is an IN operator, we also have a "addrNxt" label that
  ** means to continue with the next IN value combination.  When
  ** there are no IN operators in the constraints, the "addrNxt" label
  ** is the same as "addrBrk".
  */
  addrBrk = pLevel->addrBrk = pLevel->addrNxt = sqlite3VdbeMakeLabel(v);
  addrCont = pLevel->addrCont = sqlite3VdbeMakeLabel(v);

  /* If this is the right table of a LEFT OUTER JOIN, allocate and
  ** initialize a memory cell that records if this table matches any
  ** row of the left table of the join.
  */
  if( pLevel->iFrom>0 && (pTabItem[0].jointype & JT_LEFT)!=0 ){
    pLevel->iLeftJoin = ++pParse->nMem;
    sqlite3VdbeAddOp2(v, OP_Integer, 0, pLevel->iLeftJoin);
    VdbeComment((v, "init LEFT JOIN no-match flag"));
  }

  /* Special case of a FROM clause subquery implemented as a co-routine */
  if( pTabItem->viaCoroutine ){
    int regYield = pTabItem->regReturn;
    sqlite3VdbeAddOp3(v, OP_InitCoroutine, regYield, 0, pTabItem->addrFillSub);
    pLevel->p2 =  sqlite3VdbeAddOp2(v, OP_Yield, regYield, addrBrk);
    VdbeCoverage(v);
    VdbeComment((v, "next row of \"%s\"", pTabItem->pTab->zName));
    pLevel->op = OP_Goto;
  }else

#ifndef SQLITE_OMIT_VIRTUALTABLE
  if(  (pLoop->wsFlags & WHERE_VIRTUALTABLE)!=0 ){
    /* Case 1:  The table is a virtual-table.  Use the VFilter and VNext
    **          to access the data.
    */
    int iReg;   /* P3 Value for OP_VFilter */
    int addrNotFound;
    int nConstraint = pLoop->nLTerm;

    sqlite3ExprCachePush(pParse);
    iReg = sqlite3GetTempRange(pParse, nConstraint+2);
    addrNotFound = pLevel->addrBrk;
    for(j=0; j<nConstraint; j++){
      int iTarget = iReg+j+2;
      pTerm = pLoop->aLTerm[j];
      if( pTerm==0 ) continue;
      if( pTerm->eOperator & WO_IN ){
        codeEqualityTerm(pParse, pTerm, pLevel, j, bRev, iTarget);
        addrNotFound = pLevel->addrNxt;
      }else{
        sqlite3ExprCode(pParse, pTerm->pExpr->pRight, iTarget);
      }
    }
    sqlite3VdbeAddOp2(v, OP_Integer, pLoop->u.vtab.idxNum, iReg);
    sqlite3VdbeAddOp2(v, OP_Integer, nConstraint, iReg+1);
    sqlite3VdbeAddOp4(v, OP_VFilter, iCur, addrNotFound, iReg,
                      pLoop->u.vtab.idxStr,
                      pLoop->u.vtab.needFree ? P4_MPRINTF : P4_STATIC);
    VdbeCoverage(v);
    pLoop->u.vtab.needFree = 0;
    for(j=0; j<nConstraint && j<16; j++){
      if( (pLoop->u.vtab.omitMask>>j)&1 ){
        disableTerm(pLevel, pLoop->aLTerm[j]);
      }
    }
    pLevel->op = OP_VNext;
    pLevel->p1 = iCur;
    pLevel->p2 = sqlite3VdbeCurrentAddr(v);
    sqlite3ReleaseTempRange(pParse, iReg, nConstraint+2);
    sqlite3ExprCachePop(pParse);
  }else
#endif /* SQLITE_OMIT_VIRTUALTABLE */

  if( (pLoop->wsFlags & WHERE_IPK)!=0
   && (pLoop->wsFlags & (WHERE_COLUMN_IN|WHERE_COLUMN_EQ))!=0
  ){
    /* Case 2:  We can directly reference a single row using an
    **          equality comparison against the ROWID field.  Or
    **          we reference multiple rows using a "rowid IN (...)"
    **          construct.
    */
    assert( pLoop->u.btree.nEq==1 );
    pTerm = pLoop->aLTerm[0];
    assert( pTerm!=0 );
    assert( pTerm->pExpr!=0 );
    assert( omitTable==0 );
    testcase( pTerm->wtFlags & TERM_VIRTUAL );
    iReleaseReg = ++pParse->nMem;
    iRowidReg = codeEqualityTerm(pParse, pTerm, pLevel, 0, bRev, iReleaseReg);
    if( iRowidReg!=iReleaseReg ) sqlite3ReleaseTempReg(pParse, iReleaseReg);
    addrNxt = pLevel->addrNxt;
    sqlite3VdbeAddOp2(v, OP_MustBeInt, iRowidReg, addrNxt); VdbeCoverage(v);
    sqlite3VdbeAddOp3(v, OP_NotExists, iCur, addrNxt, iRowidReg);
    VdbeCoverage(v);
    sqlite3ExprCacheAffinityChange(pParse, iRowidReg, 1);
    sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
    VdbeComment((v, "pk"));
    pLevel->op = OP_Noop;
  }else if( (pLoop->wsFlags & WHERE_IPK)!=0
         && (pLoop->wsFlags & WHERE_COLUMN_RANGE)!=0
  ){
    /* Case 3:  We have an inequality comparison against the ROWID field.
    */
    int testOp = OP_Noop;
    int start;
    int memEndValue = 0;
    WhereTerm *pStart, *pEnd;

    assert( omitTable==0 );
    j = 0;
    pStart = pEnd = 0;
    if( pLoop->wsFlags & WHERE_BTM_LIMIT ) pStart = pLoop->aLTerm[j++];
    if( pLoop->wsFlags & WHERE_TOP_LIMIT ) pEnd = pLoop->aLTerm[j++];
    assert( pStart!=0 || pEnd!=0 );
    if( bRev ){
      pTerm = pStart;
      pStart = pEnd;
      pEnd = pTerm;
    }
    if( pStart ){
      Expr *pX;             /* The expression that defines the start bound */
      int r1, rTemp;        /* Registers for holding the start boundary */

      /* The following constant maps TK_xx codes into corresponding 
      ** seek opcodes.  It depends on a particular ordering of TK_xx
      */
      const u8 aMoveOp[] = {
           /* TK_GT */  OP_SeekGT,
           /* TK_LE */  OP_SeekLE,
           /* TK_LT */  OP_SeekLT,
           /* TK_GE */  OP_SeekGE
      };
      assert( TK_LE==TK_GT+1 );      /* Make sure the ordering.. */
      assert( TK_LT==TK_GT+2 );      /*  ... of the TK_xx values... */
      assert( TK_GE==TK_GT+3 );      /*  ... is correcct. */

      assert( (pStart->wtFlags & TERM_VNULL)==0 );
      testcase( pStart->wtFlags & TERM_VIRTUAL );
      pX = pStart->pExpr;
      assert( pX!=0 );
      testcase( pStart->leftCursor!=iCur ); /* transitive constraints */
      r1 = sqlite3ExprCodeTemp(pParse, pX->pRight, &rTemp);
      sqlite3VdbeAddOp3(v, aMoveOp[pX->op-TK_GT], iCur, addrBrk, r1);
      VdbeComment((v, "pk"));
      VdbeCoverageIf(v, pX->op==TK_GT);
      VdbeCoverageIf(v, pX->op==TK_LE);
      VdbeCoverageIf(v, pX->op==TK_LT);
      VdbeCoverageIf(v, pX->op==TK_GE);
      sqlite3ExprCacheAffinityChange(pParse, r1, 1);
      sqlite3ReleaseTempReg(pParse, rTemp);
      disableTerm(pLevel, pStart);
    }else{
      sqlite3VdbeAddOp2(v, bRev ? OP_Last : OP_Rewind, iCur, addrBrk);
      VdbeCoverageIf(v, bRev==0);
      VdbeCoverageIf(v, bRev!=0);
    }
    if( pEnd ){
      Expr *pX;
      pX = pEnd->pExpr;
      assert( pX!=0 );
      assert( (pEnd->wtFlags & TERM_VNULL)==0 );
      testcase( pEnd->leftCursor!=iCur ); /* Transitive constraints */
      testcase( pEnd->wtFlags & TERM_VIRTUAL );
      memEndValue = ++pParse->nMem;
      sqlite3ExprCode(pParse, pX->pRight, memEndValue);
      if( pX->op==TK_LT || pX->op==TK_GT ){
        testOp = bRev ? OP_Le : OP_Ge;
      }else{
        testOp = bRev ? OP_Lt : OP_Gt;
      }
      disableTerm(pLevel, pEnd);
    }
    start = sqlite3VdbeCurrentAddr(v);
    pLevel->op = bRev ? OP_Prev : OP_Next;
    pLevel->p1 = iCur;
    pLevel->p2 = start;
    assert( pLevel->p5==0 );
    if( testOp!=OP_Noop ){
      iRowidReg = ++pParse->nMem;
      sqlite3VdbeAddOp2(v, OP_Rowid, iCur, iRowidReg);
      sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
      sqlite3VdbeAddOp3(v, testOp, memEndValue, addrBrk, iRowidReg);
      VdbeCoverageIf(v, testOp==OP_Le);
      VdbeCoverageIf(v, testOp==OP_Lt);
      VdbeCoverageIf(v, testOp==OP_Ge);
      VdbeCoverageIf(v, testOp==OP_Gt);
      sqlite3VdbeChangeP5(v, SQLITE_AFF_NUMERIC | SQLITE_JUMPIFNULL);
    }
  }else if( pLoop->wsFlags & WHERE_INDEXED ){
    /* Case 4: A scan using an index.
    **
    **         The WHERE clause may contain zero or more equality 
    **         terms ("==" or "IN" operators) that refer to the N
    **         left-most columns of the index. It may also contain
    **         inequality constraints (>, <, >= or <=) on the indexed
    **         column that immediately follows the N equalities. Only 
    **         the right-most column can be an inequality - the rest must
    **         use the "==" and "IN" operators. For example, if the 
    **         index is on (x,y,z), then the following clauses are all 
    **         optimized:
    **
    **            x=5
    **            x=5 AND y=10
    **            x=5 AND y<10
    **            x=5 AND y>5 AND y<10
    **            x=5 AND y=5 AND z<=10
    **
    **         The z<10 term of the following cannot be used, only
    **         the x=5 term:
    **
    **            x=5 AND z<10
    **
    **         N may be zero if there are inequality constraints.
    **         If there are no inequality constraints, then N is at
    **         least one.
    **
    **         This case is also used when there are no WHERE clause
    **         constraints but an index is selected anyway, in order
    **         to force the output order to conform to an ORDER BY.
    */  
    static const u8 aStartOp[] = {
      0,
      0,
      OP_Rewind,           /* 2: (!start_constraints && startEq &&  !bRev) */
      OP_Last,             /* 3: (!start_constraints && startEq &&   bRev) */
      OP_SeekGT,           /* 4: (start_constraints  && !startEq && !bRev) */
      OP_SeekLT,           /* 5: (start_constraints  && !startEq &&  bRev) */
      OP_SeekGE,           /* 6: (start_constraints  &&  startEq && !bRev) */
      OP_SeekLE            /* 7: (start_constraints  &&  startEq &&  bRev) */
    };
    static const u8 aEndOp[] = {
      OP_IdxGE,            /* 0: (end_constraints && !bRev && !endEq) */
      OP_IdxGT,            /* 1: (end_constraints && !bRev &&  endEq) */
      OP_IdxLE,            /* 2: (end_constraints &&  bRev && !endEq) */
      OP_IdxLT,            /* 3: (end_constraints &&  bRev &&  endEq) */
    };
    u16 nEq = pLoop->u.btree.nEq;     /* Number of == or IN terms */
    int regBase;                 /* Base register holding constraint values */
    WhereTerm *pRangeStart = 0;  /* Inequality constraint at range start */
    WhereTerm *pRangeEnd = 0;    /* Inequality constraint at range end */
    int startEq;                 /* True if range start uses ==, >= or <= */
    int endEq;                   /* True if range end uses ==, >= or <= */
    int start_constraints;       /* Start of range is constrained */
    int nConstraint;             /* Number of constraint terms */
    Index *pIdx;                 /* The index we will be using */
    int iIdxCur;                 /* The VDBE cursor for the index */
    int nExtraReg = 0;           /* Number of extra registers needed */
    int op;                      /* Instruction opcode */
    char *zStartAff;             /* Affinity for start of range constraint */
    char cEndAff = 0;            /* Affinity for end of range constraint */
    u8 bSeekPastNull = 0;        /* True to seek past initial nulls */
    u8 bStopAtNull = 0;          /* Add condition to terminate at NULLs */

    pIdx = pLoop->u.btree.pIndex;
    iIdxCur = pLevel->iIdxCur;
    assert( nEq>=pLoop->nSkip );

    /* If this loop satisfies a sort order (pOrderBy) request that 
    ** was passed to this function to implement a "SELECT min(x) ..." 
    ** query, then the caller will only allow the loop to run for
    ** a single iteration. This means that the first row returned
    ** should not have a NULL value stored in 'x'. If column 'x' is
    ** the first one after the nEq equality constraints in the index,
    ** this requires some special handling.
    */
    assert( pWInfo->pOrderBy==0
         || pWInfo->pOrderBy->nExpr==1
         || (pWInfo->wctrlFlags&WHERE_ORDERBY_MIN)==0 );
    if( (pWInfo->wctrlFlags&WHERE_ORDERBY_MIN)!=0
     && pWInfo->nOBSat>0
     && (pIdx->nKeyCol>nEq)
    ){
      assert( pLoop->nSkip==0 );
      bSeekPastNull = 1;
      nExtraReg = 1;
    }

    /* Find any inequality constraint terms for the start and end 
    ** of the range. 
    */
    j = nEq;
    if( pLoop->wsFlags & WHERE_BTM_LIMIT ){
      pRangeStart = pLoop->aLTerm[j++];
      nExtraReg = 1;
      /* Like optimization range constraints always occur in pairs */
      assert( (pRangeStart->wtFlags & TERM_LIKEOPT)==0 || 
              (pLoop->wsFlags & WHERE_TOP_LIMIT)!=0 );
    }
    if( pLoop->wsFlags & WHERE_TOP_LIMIT ){
      pRangeEnd = pLoop->aLTerm[j++];
      nExtraReg = 1;
      if( (pRangeEnd->wtFlags & TERM_LIKEOPT)!=0 ){
        assert( pRangeStart!=0 );                     /* LIKE opt constraints */
        assert( pRangeStart->wtFlags & TERM_LIKEOPT );   /* occur in pairs */
        pLevel->iLikeRepCntr = ++pParse->nMem;
        testcase( bRev );
        testcase( pIdx->aSortOrder[nEq]==SQLITE_SO_DESC );
        sqlite3VdbeAddOp2(v, OP_Integer,
                          bRev ^ (pIdx->aSortOrder[nEq]==SQLITE_SO_DESC),
                          pLevel->iLikeRepCntr);
        VdbeComment((v, "LIKE loop counter"));
        pLevel->addrLikeRep = sqlite3VdbeCurrentAddr(v);
      }
      if( pRangeStart==0
       && (j = pIdx->aiColumn[nEq])>=0 
       && pIdx->pTable->aCol[j].notNull==0
      ){
        bSeekPastNull = 1;
      }
    }
    assert( pRangeEnd==0 || (pRangeEnd->wtFlags & TERM_VNULL)==0 );

    /* Generate code to evaluate all constraint terms using == or IN
    ** and store the values of those terms in an array of registers
    ** starting at regBase.
    */
    regBase = codeAllEqualityTerms(pParse,pLevel,bRev,nExtraReg,&zStartAff);
    assert( zStartAff==0 || sqlite3Strlen30(zStartAff)>=nEq );
    if( zStartAff ) cEndAff = zStartAff[nEq];
    addrNxt = pLevel->addrNxt;

    /* If we are doing a reverse order scan on an ascending index, or
    ** a forward order scan on a descending index, interchange the 
    ** start and end terms (pRangeStart and pRangeEnd).
    */
    if( (nEq<pIdx->nKeyCol && bRev==(pIdx->aSortOrder[nEq]==SQLITE_SO_ASC))
     || (bRev && pIdx->nKeyCol==nEq)
    ){
      SWAP(WhereTerm *, pRangeEnd, pRangeStart);
      SWAP(u8, bSeekPastNull, bStopAtNull);
    }

    testcase( pRangeStart && (pRangeStart->eOperator & WO_LE)!=0 );
    testcase( pRangeStart && (pRangeStart->eOperator & WO_GE)!=0 );
    testcase( pRangeEnd && (pRangeEnd->eOperator & WO_LE)!=0 );
    testcase( pRangeEnd && (pRangeEnd->eOperator & WO_GE)!=0 );
    startEq = !pRangeStart || pRangeStart->eOperator & (WO_LE|WO_GE);
    endEq =   !pRangeEnd || pRangeEnd->eOperator & (WO_LE|WO_GE);
    start_constraints = pRangeStart || nEq>0;

    /* Seek the index cursor to the start of the range. */
    nConstraint = nEq;
    if( pRangeStart ){
      Expr *pRight = pRangeStart->pExpr->pRight;
      sqlite3ExprCode(pParse, pRight, regBase+nEq);
      whereLikeOptimizationStringFixup(v, pLevel, pRangeStart);
      if( (pRangeStart->wtFlags & TERM_VNULL)==0
       && sqlite3ExprCanBeNull(pRight)
      ){
        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
        VdbeCoverage(v);
      }
      if( zStartAff ){
        if( sqlite3CompareAffinity(pRight, zStartAff[nEq])==SQLITE_AFF_BLOB){
          /* Since the comparison is to be performed with no conversions
          ** applied to the operands, set the affinity to apply to pRight to 
          ** SQLITE_AFF_BLOB.  */
          zStartAff[nEq] = SQLITE_AFF_BLOB;
        }
        if( sqlite3ExprNeedsNoAffinityChange(pRight, zStartAff[nEq]) ){
          zStartAff[nEq] = SQLITE_AFF_BLOB;
        }
      }  
      nConstraint++;
      testcase( pRangeStart->wtFlags & TERM_VIRTUAL );
    }else if( bSeekPastNull ){
      sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
      nConstraint++;
      startEq = 0;
      start_constraints = 1;
    }
    codeApplyAffinity(pParse, regBase, nConstraint - bSeekPastNull, zStartAff);
    op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
    assert( op!=0 );
    sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
    VdbeCoverage(v);
    VdbeCoverageIf(v, op==OP_Rewind);  testcase( op==OP_Rewind );
    VdbeCoverageIf(v, op==OP_Last);    testcase( op==OP_Last );
    VdbeCoverageIf(v, op==OP_SeekGT);  testcase( op==OP_SeekGT );
    VdbeCoverageIf(v, op==OP_SeekGE);  testcase( op==OP_SeekGE );
    VdbeCoverageIf(v, op==OP_SeekLE);  testcase( op==OP_SeekLE );
    VdbeCoverageIf(v, op==OP_SeekLT);  testcase( op==OP_SeekLT );

    /* Load the value for the inequality constraint at the end of the
    ** range (if any).
    */
    nConstraint = nEq;
    if( pRangeEnd ){
      Expr *pRight = pRangeEnd->pExpr->pRight;
      sqlite3ExprCacheRemove(pParse, regBase+nEq, 1);
      sqlite3ExprCode(pParse, pRight, regBase+nEq);
      whereLikeOptimizationStringFixup(v, pLevel, pRangeEnd);
      if( (pRangeEnd->wtFlags & TERM_VNULL)==0
       && sqlite3ExprCanBeNull(pRight)
      ){
        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
        VdbeCoverage(v);
      }
      if( sqlite3CompareAffinity(pRight, cEndAff)!=SQLITE_AFF_BLOB
       && !sqlite3ExprNeedsNoAffinityChange(pRight, cEndAff)
      ){
        codeApplyAffinity(pParse, regBase+nEq, 1, &cEndAff);
      }
      nConstraint++;
      testcase( pRangeEnd->wtFlags & TERM_VIRTUAL );
    }else if( bStopAtNull ){
      sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
      endEq = 0;
      nConstraint++;
    }
    sqlite3DbFree(db, zStartAff);

    /* Top of the loop body */
    pLevel->p2 = sqlite3VdbeCurrentAddr(v);

    /* Check if the index cursor is past the end of the range. */
    if( nConstraint ){
      op = aEndOp[bRev*2 + endEq];
      sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
      testcase( op==OP_IdxGT );  VdbeCoverageIf(v, op==OP_IdxGT );
      testcase( op==OP_IdxGE );  VdbeCoverageIf(v, op==OP_IdxGE );
      testcase( op==OP_IdxLT );  VdbeCoverageIf(v, op==OP_IdxLT );
      testcase( op==OP_IdxLE );  VdbeCoverageIf(v, op==OP_IdxLE );
    }

    /* Seek the table cursor, if required */
    disableTerm(pLevel, pRangeStart);
    disableTerm(pLevel, pRangeEnd);
    if( omitTable ){
      /* pIdx is a covering index.  No need to access the main table. */
    }else if( HasRowid(pIdx->pTable) ){
      iRowidReg = ++pParse->nMem;
      sqlite3VdbeAddOp2(v, OP_IdxRowid, iIdxCur, iRowidReg);
      sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
      sqlite3VdbeAddOp2(v, OP_Seek, iCur, iRowidReg);  /* Deferred seek */
    }else if( iCur!=iIdxCur ){
      Index *pPk = sqlite3PrimaryKeyIndex(pIdx->pTable);
      iRowidReg = sqlite3GetTempRange(pParse, pPk->nKeyCol);
      for(j=0; j<pPk->nKeyCol; j++){
        k = sqlite3ColumnOfIndex(pIdx, pPk->aiColumn[j]);
        sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, k, iRowidReg+j);
      }
      sqlite3VdbeAddOp4Int(v, OP_NotFound, iCur, addrCont,
                           iRowidReg, pPk->nKeyCol); VdbeCoverage(v);
    }

    /* Record the instruction used to terminate the loop. Disable 
    ** WHERE clause terms made redundant by the index range scan.
    */
    if( pLoop->wsFlags & WHERE_ONEROW ){
      pLevel->op = OP_Noop;
    }else if( bRev ){
      pLevel->op = OP_Prev;
    }else{
      pLevel->op = OP_Next;
    }
    pLevel->p1 = iIdxCur;
    pLevel->p3 = (pLoop->wsFlags&WHERE_UNQ_WANTED)!=0 ? 1:0;
    if( (pLoop->wsFlags & WHERE_CONSTRAINT)==0 ){
      pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
    }else{
      assert( pLevel->p5==0 );
    }
  }else

#ifndef SQLITE_OMIT_OR_OPTIMIZATION
  if( pLoop->wsFlags & WHERE_MULTI_OR ){
    /* Case 5:  Two or more separately indexed terms connected by OR
    **
    ** Example:
    **
    **   CREATE TABLE t1(a,b,c,d);
    **   CREATE INDEX i1 ON t1(a);
    **   CREATE INDEX i2 ON t1(b);
    **   CREATE INDEX i3 ON t1(c);
    **
    **   SELECT * FROM t1 WHERE a=5 OR b=7 OR (c=11 AND d=13)
    **
    ** In the example, there are three indexed terms connected by OR.
    ** The top of the loop looks like this:
    **
    **          Null       1                # Zero the rowset in reg 1
    **
    ** Then, for each indexed term, the following. The arguments to
    ** RowSetTest are such that the rowid of the current row is inserted
    ** into the RowSet. If it is already present, control skips the
    ** Gosub opcode and jumps straight to the code generated by WhereEnd().
    **
    **        sqlite3WhereBegin(<term>)
    **          RowSetTest                  # Insert rowid into rowset
    **          Gosub      2 A
    **        sqlite3WhereEnd()
    **
    ** Following the above, code to terminate the loop. Label A, the target
    ** of the Gosub above, jumps to the instruction right after the Goto.
    **
    **          Null       1                # Zero the rowset in reg 1
    **          Goto       B                # The loop is finished.
    **
    **       A: <loop body>                 # Return data, whatever.
    **
    **          Return     2                # Jump back to the Gosub
    **
    **       B: <after the loop>
    **
    ** Added 2014-05-26: If the table is a WITHOUT ROWID table, then
    ** use an ephemeral index instead of a RowSet to record the primary
    ** keys of the rows we have already seen.
    **
    */
    WhereClause *pOrWc;    /* The OR-clause broken out into subterms */
    SrcList *pOrTab;       /* Shortened table list or OR-clause generation */
    Index *pCov = 0;             /* Potential covering index (or NULL) */
    int iCovCur = pParse->nTab++;  /* Cursor used for index scans (if any) */

    int regReturn = ++pParse->nMem;           /* Register used with OP_Gosub */
    int regRowset = 0;                        /* Register for RowSet object */
    int regRowid = 0;                         /* Register holding rowid */
    int iLoopBody = sqlite3VdbeMakeLabel(v);  /* Start of loop body */
    int iRetInit;                             /* Address of regReturn init */
    int untestedTerms = 0;             /* Some terms not completely tested */
    int ii;                            /* Loop counter */
    u16 wctrlFlags;                    /* Flags for sub-WHERE clause */
    Expr *pAndExpr = 0;                /* An ".. AND (...)" expression */
    Table *pTab = pTabItem->pTab;
   
    pTerm = pLoop->aLTerm[0];
    assert( pTerm!=0 );
    assert( pTerm->eOperator & WO_OR );
    assert( (pTerm->wtFlags & TERM_ORINFO)!=0 );
    pOrWc = &pTerm->u.pOrInfo->wc;
    pLevel->op = OP_Return;
    pLevel->p1 = regReturn;

    /* Set up a new SrcList in pOrTab containing the table being scanned
    ** by this loop in the a[0] slot and all notReady tables in a[1..] slots.
    ** This becomes the SrcList in the recursive call to sqlite3WhereBegin().
    */
    if( pWInfo->nLevel>1 ){
      int nNotReady;                 /* The number of notReady tables */
      struct SrcList_item *origSrc;     /* Original list of tables */
      nNotReady = pWInfo->nLevel - iLevel - 1;
      pOrTab = sqlite3StackAllocRaw(db,
                            sizeof(*pOrTab)+ nNotReady*sizeof(pOrTab->a[0]));
      if( pOrTab==0 ) return notReady;
      pOrTab->nAlloc = (u8)(nNotReady + 1);
      pOrTab->nSrc = pOrTab->nAlloc;
      memcpy(pOrTab->a, pTabItem, sizeof(*pTabItem));
      origSrc = pWInfo->pTabList->a;
      for(k=1; k<=nNotReady; k++){
        memcpy(&pOrTab->a[k], &origSrc[pLevel[k].iFrom], sizeof(pOrTab->a[k]));
      }
    }else{
      pOrTab = pWInfo->pTabList;
    }

    /* Initialize the rowset register to contain NULL. An SQL NULL is 
    ** equivalent to an empty rowset.  Or, create an ephemeral index
    ** capable of holding primary keys in the case of a WITHOUT ROWID.
    **
    ** Also initialize regReturn to contain the address of the instruction 
    ** immediately following the OP_Return at the bottom of the loop. This
    ** is required in a few obscure LEFT JOIN cases where control jumps
    ** over the top of the loop into the body of it. In this case the 
    ** correct response for the end-of-loop code (the OP_Return) is to 
    ** fall through to the next instruction, just as an OP_Next does if
    ** called on an uninitialized cursor.
    */
    if( (pWInfo->wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
      if( HasRowid(pTab) ){
        regRowset = ++pParse->nMem;
        sqlite3VdbeAddOp2(v, OP_Null, 0, regRowset);
      }else{
        Index *pPk = sqlite3PrimaryKeyIndex(pTab);
        regRowset = pParse->nTab++;
        sqlite3VdbeAddOp2(v, OP_OpenEphemeral, regRowset, pPk->nKeyCol);
        sqlite3VdbeSetP4KeyInfo(pParse, pPk);
      }
      regRowid = ++pParse->nMem;
    }
    iRetInit = sqlite3VdbeAddOp2(v, OP_Integer, 0, regReturn);

    /* If the original WHERE clause is z of the form:  (x1 OR x2 OR ...) AND y
    ** Then for every term xN, evaluate as the subexpression: xN AND z
    ** That way, terms in y that are factored into the disjunction will
    ** be picked up by the recursive calls to sqlite3WhereBegin() below.
    **
    ** Actually, each subexpression is converted to "xN AND w" where w is
    ** the "interesting" terms of z - terms that did not originate in the
    ** ON or USING clause of a LEFT JOIN, and terms that are usable as 
    ** indices.
    **
    ** This optimization also only applies if the (x1 OR x2 OR ...) term
    ** is not contained in the ON clause of a LEFT JOIN.
    ** See ticket http://www.sqlite.org/src/info/f2369304e4
    */
    if( pWC->nTerm>1 ){
      int iTerm;
      for(iTerm=0; iTerm<pWC->nTerm; iTerm++){
        Expr *pExpr = pWC->a[iTerm].pExpr;
        if( &pWC->a[iTerm] == pTerm ) continue;
        if( ExprHasProperty(pExpr, EP_FromJoin) ) continue;
        if( (pWC->a[iTerm].wtFlags & TERM_VIRTUAL)!=0 ) continue;
        if( (pWC->a[iTerm].eOperator & WO_ALL)==0 ) continue;
        testcase( pWC->a[iTerm].wtFlags & TERM_ORINFO );
        pExpr = sqlite3ExprDup(db, pExpr, 0);
        pAndExpr = sqlite3ExprAnd(db, pAndExpr, pExpr);
      }
      if( pAndExpr ){
        pAndExpr = sqlite3PExpr(pParse, TK_AND, 0, pAndExpr, 0);
      }
    }

    /* Run a separate WHERE clause for each term of the OR clause.  After
    ** eliminating duplicates from other WHERE clauses, the action for each
    ** sub-WHERE clause is to to invoke the main loop body as a subroutine.
    */
    wctrlFlags =  WHERE_OMIT_OPEN_CLOSE
                | WHERE_FORCE_TABLE
                | WHERE_ONETABLE_ONLY
                | WHERE_NO_AUTOINDEX;
    for(ii=0; ii<pOrWc->nTerm; ii++){
      WhereTerm *pOrTerm = &pOrWc->a[ii];
      if( pOrTerm->leftCursor==iCur || (pOrTerm->eOperator & WO_AND)!=0 ){
        WhereInfo *pSubWInfo;           /* Info for single OR-term scan */
        Expr *pOrExpr = pOrTerm->pExpr; /* Current OR clause term */
        int j1 = 0;                     /* Address of jump operation */
        if( pAndExpr && !ExprHasProperty(pOrExpr, EP_FromJoin) ){
          pAndExpr->pLeft = pOrExpr;
          pOrExpr = pAndExpr;
        }
        /* Loop through table entries that match term pOrTerm. */
        WHERETRACE(0xffff, ("Subplan for OR-clause:\n"));
        pSubWInfo = sqlite3WhereBegin(pParse, pOrTab, pOrExpr, 0, 0,
                                      wctrlFlags, iCovCur);
        assert( pSubWInfo || pParse->nErr || db->mallocFailed );
        if( pSubWInfo ){
          WhereLoop *pSubLoop;
          int addrExplain = sqlite3WhereExplainOneScan(
              pParse, pOrTab, &pSubWInfo->a[0], iLevel, pLevel->iFrom, 0
          );
          sqlite3WhereAddScanStatus(v, pOrTab, &pSubWInfo->a[0], addrExplain);

          /* This is the sub-WHERE clause body.  First skip over
          ** duplicate rows from prior sub-WHERE clauses, and record the
          ** rowid (or PRIMARY KEY) for the current row so that the same
          ** row will be skipped in subsequent sub-WHERE clauses.
          */
          if( (pWInfo->wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
            int r;
            int iSet = ((ii==pOrWc->nTerm-1)?-1:ii);
            if( HasRowid(pTab) ){
              r = sqlite3ExprCodeGetColumn(pParse, pTab, -1, iCur, regRowid, 0);
              j1 = sqlite3VdbeAddOp4Int(v, OP_RowSetTest, regRowset, 0, r,iSet);
              VdbeCoverage(v);
            }else{
              Index *pPk = sqlite3PrimaryKeyIndex(pTab);
              int nPk = pPk->nKeyCol;
              int iPk;

              /* Read the PK into an array of temp registers. */
              r = sqlite3GetTempRange(pParse, nPk);
              for(iPk=0; iPk<nPk; iPk++){
                int iCol = pPk->aiColumn[iPk];
                sqlite3ExprCodeGetColumn(pParse, pTab, iCol, iCur, r+iPk, 0);
              }

              /* Check if the temp table already contains this key. If so,
              ** the row has already been included in the result set and
              ** can be ignored (by jumping past the Gosub below). Otherwise,
              ** insert the key into the temp table and proceed with processing
              ** the row.
              **
              ** Use some of the same optimizations as OP_RowSetTest: If iSet
              ** is zero, assume that the key cannot already be present in
              ** the temp table. And if iSet is -1, assume that there is no 
              ** need to insert the key into the temp table, as it will never 
              ** be tested for.  */ 
              if( iSet ){
                j1 = sqlite3VdbeAddOp4Int(v, OP_Found, regRowset, 0, r, nPk);
                VdbeCoverage(v);
              }
              if( iSet>=0 ){
                sqlite3VdbeAddOp3(v, OP_MakeRecord, r, nPk, regRowid);
                sqlite3VdbeAddOp3(v, OP_IdxInsert, regRowset, regRowid, 0);
                if( iSet ) sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
              }

              /* Release the array of temp registers */
              sqlite3ReleaseTempRange(pParse, r, nPk);
            }
          }

          /* Invoke the main loop body as a subroutine */
          sqlite3VdbeAddOp2(v, OP_Gosub, regReturn, iLoopBody);

          /* Jump here (skipping the main loop body subroutine) if the
          ** current sub-WHERE row is a duplicate from prior sub-WHEREs. */
          if( j1 ) sqlite3VdbeJumpHere(v, j1);

          /* The pSubWInfo->untestedTerms flag means that this OR term
          ** contained one or more AND term from a notReady table.  The
          ** terms from the notReady table could not be tested and will
          ** need to be tested later.
          */
          if( pSubWInfo->untestedTerms ) untestedTerms = 1;

          /* If all of the OR-connected terms are optimized using the same
          ** index, and the index is opened using the same cursor number
          ** by each call to sqlite3WhereBegin() made by this loop, it may
          ** be possible to use that index as a covering index.
          **
          ** If the call to sqlite3WhereBegin() above resulted in a scan that
          ** uses an index, and this is either the first OR-connected term
          ** processed or the index is the same as that used by all previous
          ** terms, set pCov to the candidate covering index. Otherwise, set 
          ** pCov to NULL to indicate that no candidate covering index will 
          ** be available.
          */
          pSubLoop = pSubWInfo->a[0].pWLoop;
          assert( (pSubLoop->wsFlags & WHERE_AUTO_INDEX)==0 );
          if( (pSubLoop->wsFlags & WHERE_INDEXED)!=0
           && (ii==0 || pSubLoop->u.btree.pIndex==pCov)
           && (HasRowid(pTab) || !IsPrimaryKeyIndex(pSubLoop->u.btree.pIndex))
          ){
            assert( pSubWInfo->a[0].iIdxCur==iCovCur );
            pCov = pSubLoop->u.btree.pIndex;
            wctrlFlags |= WHERE_REOPEN_IDX;
          }else{
            pCov = 0;
          }

          /* Finish the loop through table entries that match term pOrTerm. */
          sqlite3WhereEnd(pSubWInfo);
        }
      }
    }
    pLevel->u.pCovidx = pCov;
    if( pCov ) pLevel->iIdxCur = iCovCur;
    if( pAndExpr ){
      pAndExpr->pLeft = 0;
      sqlite3ExprDelete(db, pAndExpr);
    }
    sqlite3VdbeChangeP1(v, iRetInit, sqlite3VdbeCurrentAddr(v));
    sqlite3VdbeAddOp2(v, OP_Goto, 0, pLevel->addrBrk);
    sqlite3VdbeResolveLabel(v, iLoopBody);

    if( pWInfo->nLevel>1 ) sqlite3StackFree(db, pOrTab);
    if( !untestedTerms ) disableTerm(pLevel, pTerm);
  }else
#endif /* SQLITE_OMIT_OR_OPTIMIZATION */

  {
    /* Case 6:  There is no usable index.  We must do a complete
    **          scan of the entire table.
    */
    static const u8 aStep[] = { OP_Next, OP_Prev };
    static const u8 aStart[] = { OP_Rewind, OP_Last };
    assert( bRev==0 || bRev==1 );
    if( pTabItem->isRecursive ){
      /* Tables marked isRecursive have only a single row that is stored in
      ** a pseudo-cursor.  No need to Rewind or Next such cursors. */
      pLevel->op = OP_Noop;
    }else{
      pLevel->op = aStep[bRev];
      pLevel->p1 = iCur;
      pLevel->p2 = 1 + sqlite3VdbeAddOp2(v, aStart[bRev], iCur, addrBrk);
      VdbeCoverageIf(v, bRev==0);
      VdbeCoverageIf(v, bRev!=0);
      pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
    }
  }

#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
  pLevel->addrVisit = sqlite3VdbeCurrentAddr(v);
#endif

  /* Insert code to test every subexpression that can be completely
  ** computed using the current set of tables.
  */
  for(pTerm=pWC->a, j=pWC->nTerm; j>0; j--, pTerm++){
    Expr *pE;
    int skipLikeAddr = 0;
    testcase( pTerm->wtFlags & TERM_VIRTUAL );
    testcase( pTerm->wtFlags & TERM_CODED );
    if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
    if( (pTerm->prereqAll & pLevel->notReady)!=0 ){
      testcase( pWInfo->untestedTerms==0
               && (pWInfo->wctrlFlags & WHERE_ONETABLE_ONLY)!=0 );
      pWInfo->untestedTerms = 1;
      continue;
    }
    pE = pTerm->pExpr;
    assert( pE!=0 );
    if( pLevel->iLeftJoin && !ExprHasProperty(pE, EP_FromJoin) ){
      continue;
    }
    if( pTerm->wtFlags & TERM_LIKECOND ){
      assert( pLevel->iLikeRepCntr>0 );
      skipLikeAddr = sqlite3VdbeAddOp1(v, OP_IfNot, pLevel->iLikeRepCntr);
      VdbeCoverage(v);
    }
    sqlite3ExprIfFalse(pParse, pE, addrCont, SQLITE_JUMPIFNULL);
    if( skipLikeAddr ) sqlite3VdbeJumpHere(v, skipLikeAddr);
    pTerm->wtFlags |= TERM_CODED;
  }

  /* Insert code to test for implied constraints based on transitivity
  ** of the "==" operator.
  **
  ** Example: If the WHERE clause contains "t1.a=t2.b" and "t2.b=123"
  ** and we are coding the t1 loop and the t2 loop has not yet coded,
  ** then we cannot use the "t1.a=t2.b" constraint, but we can code
  ** the implied "t1.a=123" constraint.
  */
  for(pTerm=pWC->a, j=pWC->nTerm; j>0; j--, pTerm++){
    Expr *pE, *pEAlt;
    WhereTerm *pAlt;
    if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
    if( (pTerm->eOperator & (WO_EQ|WO_IS))==0 ) continue;
    if( (pTerm->eOperator & WO_EQUIV)==0 ) continue;
    if( pTerm->leftCursor!=iCur ) continue;
    if( pLevel->iLeftJoin ) continue;
    pE = pTerm->pExpr;
    assert( !ExprHasProperty(pE, EP_FromJoin) );
    assert( (pTerm->prereqRight & pLevel->notReady)!=0 );
    pAlt = sqlite3WhereFindTerm(pWC, iCur, pTerm->u.leftColumn, notReady,
                    WO_EQ|WO_IN|WO_IS, 0);
    if( pAlt==0 ) continue;
    if( pAlt->wtFlags & (TERM_CODED) ) continue;
    testcase( pAlt->eOperator & WO_EQ );
    testcase( pAlt->eOperator & WO_IS );
    testcase( pAlt->eOperator & WO_IN );
    VdbeModuleComment((v, "begin transitive constraint"));
    pEAlt = sqlite3StackAllocRaw(db, sizeof(*pEAlt));
    if( pEAlt ){
      *pEAlt = *pAlt->pExpr;
      pEAlt->pLeft = pE->pLeft;
      sqlite3ExprIfFalse(pParse, pEAlt, addrCont, SQLITE_JUMPIFNULL);
      sqlite3StackFree(db, pEAlt);
    }
  }

  /* For a LEFT OUTER JOIN, generate code that will record the fact that
  ** at least one row of the right table has matched the left table.  
  */
  if( pLevel->iLeftJoin ){
    pLevel->addrFirst = sqlite3VdbeCurrentAddr(v);
    sqlite3VdbeAddOp2(v, OP_Integer, 1, pLevel->iLeftJoin);
    VdbeComment((v, "record LEFT JOIN hit"));
    sqlite3ExprCacheClear(pParse);
    for(pTerm=pWC->a, j=0; j<pWC->nTerm; j++, pTerm++){
      testcase( pTerm->wtFlags & TERM_VIRTUAL );
      testcase( pTerm->wtFlags & TERM_CODED );
      if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
      if( (pTerm->prereqAll & pLevel->notReady)!=0 ){
        assert( pWInfo->untestedTerms );
        continue;
      }
      assert( pTerm->pExpr );
      sqlite3ExprIfFalse(pParse, pTerm->pExpr, addrCont, SQLITE_JUMPIFNULL);
      pTerm->wtFlags |= TERM_CODED;
    }
  }

  return pLevel->notReady;
}
Changes to tool/mksqlite3c.tcl.
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   prepare.c
   select.c
   table.c
   trigger.c
   update.c
   vacuum.c
   vtab.c

   where.c

   parse.c

   tokenize.c
   complete.c








>







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   prepare.c
   select.c
   table.c
   trigger.c
   update.c
   vacuum.c
   vtab.c
   wherecode.c
   where.c

   parse.c

   tokenize.c
   complete.c