**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code routines that are called by the parser
** in order to generate code for DELETE FROM statements.
**
** $Id: delete.c,v 1.190 2008/12/10 21:19:57 drh Exp $
*/
#include "sqliteInt.h"

/*
** Look up every table that is named in pSrc.  If any table is not found,
** add an error message to pParse->zErrMsg and return NULL.  If all tables
** are found, return a pointer to the last table.
................................................................................
  /* The usual case: There is a WHERE clause so we have to scan through
  ** the table and pick which records to delete.
  */
  {
    int iRowid = ++pParse->nMem;    /* Used for storing rowid values. */
    int iRowSet = ++pParse->nMem;   /* Register for rowset of rows to delete */

    /* Begin the database scan
    */

    pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, 0, 0);

    if( pWInfo==0 ) goto delete_from_cleanup;

    /* Remember the rowid of every item to be deleted.
    */
    sqlite3VdbeAddOp2(v, IsVirtual(pTab) ? OP_VRowid : OP_Rowid, iCur, iRowid);
    sqlite3VdbeAddOp2(v, OP_RowSetAdd, iRowSet, iRowid);
    if( db->flags & SQLITE_CountRows ){
      sqlite3VdbeAddOp2(v, OP_AddImm, memCnt, 1);
    }

    /* End the database scan loop.
    */
    sqlite3WhereEnd(pWInfo);

    /* Open the pseudo-table used to store OLD if there are triggers.
    */
    if( triggers_exist ){
      sqlite3VdbeAddOp2(v, OP_SetNumColumns, 0, pTab->nCol);
      sqlite3VdbeAddOp1(v, OP_OpenPseudo, oldIdx);

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code routines that are called by the parser
** in order to generate code for DELETE FROM statements.
**
** $Id: delete.c,v 1.191 2008/12/23 23:56:22 drh Exp $
*/
#include "sqliteInt.h"

/*
** Look up every table that is named in pSrc.  If any table is not found,
** add an error message to pParse->zErrMsg and return NULL.  If all tables
** are found, return a pointer to the last table.
................................................................................
  /* The usual case: There is a WHERE clause so we have to scan through
  ** the table and pick which records to delete.
  */
  {
    int iRowid = ++pParse->nMem;    /* Used for storing rowid values. */
    int iRowSet = ++pParse->nMem;   /* Register for rowset of rows to delete */

    /* Collect rowids of every row to be deleted.
    */
    sqlite3VdbeAddOp2(v, OP_Null, 0, iRowSet);
    pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, 0,
                               WHERE_FILL_ROWSET, iRowSet);
    if( pWInfo==0 ) goto delete_from_cleanup;





    if( db->flags & SQLITE_CountRows ){
      sqlite3VdbeAddOp2(v, OP_AddImm, memCnt, 1);
    }



    sqlite3WhereEnd(pWInfo);

    /* Open the pseudo-table used to store OLD if there are triggers.
    */
    if( triggers_exist ){
      sqlite3VdbeAddOp2(v, OP_SetNumColumns, 0, pTab->nCol);
      sqlite3VdbeAddOp1(v, OP_OpenPseudo, oldIdx);

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code routines that are called by the parser
** to handle SELECT statements in SQLite.
**
** $Id: select.c,v 1.494 2008/12/10 22:15:00 drh Exp $
*/
#include "sqliteInt.h"


/*
** Delete all the content of a Select structure but do not deallocate
** the select structure itself.
................................................................................
  }

  /* Aggregate and non-aggregate queries are handled differently */
  if( !isAgg && pGroupBy==0 ){
    /* This case is for non-aggregate queries
    ** Begin the database scan
    */
    pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pOrderBy, 0);
    if( pWInfo==0 ) goto select_end;

    /* If sorting index that was created by a prior OP_OpenEphemeral 
    ** instruction ended up not being needed, then change the OP_OpenEphemeral
    ** into an OP_Noop.
    */
    if( addrSortIndex>=0 && pOrderBy==0 ){
................................................................................

      /* Begin a loop that will extract all source rows in GROUP BY order.
      ** This might involve two separate loops with an OP_Sort in between, or
      ** it might be a single loop that uses an index to extract information
      ** in the right order to begin with.
      */
      sqlite3VdbeAddOp2(v, OP_Gosub, regReset, addrReset);
      pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pGroupBy, 0);
      if( pWInfo==0 ) goto select_end;
      if( pGroupBy==0 ){
        /* The optimizer is able to deliver rows in group by order so
        ** we do not have to sort.  The OP_OpenEphemeral table will be
        ** cancelled later because we still need to use the pKeyInfo
        */
        pGroupBy = p->pGroupBy;
................................................................................
      }

      /* This case runs if the aggregate has no GROUP BY clause.  The
      ** processing is much simpler since there is only a single row
      ** of output.
      */
      resetAccumulator(pParse, &sAggInfo);
      pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pMinMax, flag);
      if( pWInfo==0 ){
        sqlite3ExprListDelete(db, pDel);
        goto select_end;
      }
      updateAccumulator(pParse, &sAggInfo);
      if( !pMinMax && flag ){
        sqlite3VdbeAddOp2(v, OP_Goto, 0, pWInfo->iBreak);

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code routines that are called by the parser
** to handle SELECT statements in SQLite.
**
** $Id: select.c,v 1.495 2008/12/23 23:56:22 drh Exp $
*/
#include "sqliteInt.h"


/*
** Delete all the content of a Select structure but do not deallocate
** the select structure itself.
................................................................................
  }

  /* Aggregate and non-aggregate queries are handled differently */
  if( !isAgg && pGroupBy==0 ){
    /* This case is for non-aggregate queries
    ** Begin the database scan
    */
    pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pOrderBy, 0, 0);
    if( pWInfo==0 ) goto select_end;

    /* If sorting index that was created by a prior OP_OpenEphemeral 
    ** instruction ended up not being needed, then change the OP_OpenEphemeral
    ** into an OP_Noop.
    */
    if( addrSortIndex>=0 && pOrderBy==0 ){
................................................................................

      /* Begin a loop that will extract all source rows in GROUP BY order.
      ** This might involve two separate loops with an OP_Sort in between, or
      ** it might be a single loop that uses an index to extract information
      ** in the right order to begin with.
      */
      sqlite3VdbeAddOp2(v, OP_Gosub, regReset, addrReset);
      pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pGroupBy, 0, 0);
      if( pWInfo==0 ) goto select_end;
      if( pGroupBy==0 ){
        /* The optimizer is able to deliver rows in group by order so
        ** we do not have to sort.  The OP_OpenEphemeral table will be
        ** cancelled later because we still need to use the pKeyInfo
        */
        pGroupBy = p->pGroupBy;
................................................................................
      }

      /* This case runs if the aggregate has no GROUP BY clause.  The
      ** processing is much simpler since there is only a single row
      ** of output.
      */
      resetAccumulator(pParse, &sAggInfo);
      pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pMinMax, flag, 0);
      if( pWInfo==0 ){
        sqlite3ExprListDelete(db, pDel);
        goto select_end;
      }
      updateAccumulator(pParse, &sAggInfo);
      if( !pMinMax && flag ){
        sqlite3VdbeAddOp2(v, OP_Goto, 0, pWInfo->iBreak);

**    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.
**
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.814 2008/12/23 13:35:23 drh Exp $
*/
#ifndef _SQLITEINT_H_
#define _SQLITEINT_H_

/*
** Include the configuration header output by 'configure' if we're using the
** autoconf-based build
................................................................................
  */
  sqlite3_index_info *pIdxInfo;  /* Index info for n-th source table */
};

/*
** Flags appropriate for the wctrlFlags parameter of sqlite3WhereBegin().
*/
#define WHERE_ORDERBY_NORMAL     0   /* No-op */
#define WHERE_ORDERBY_MIN        1   /* ORDER BY processing for min() func */
#define WHERE_ORDERBY_MAX        2   /* ORDER BY processing for max() func */
#define WHERE_ONEPASS_DESIRED    4   /* Want to do one-pass UPDATE/DELETE */


/*
** The WHERE clause processing routine has two halves.  The
** first part does the start of the WHERE loop and the second
** half does the tail of the WHERE loop.  An instance of
** this structure is returned by the first half and passed
** into the second half to give some continuity.
*/
struct WhereInfo {
  Parse *pParse;       /* Parsing and code generating context */
  u8 okOnePass;        /* Ok to use one-pass algorithm for UPDATE or DELETE */

  SrcList *pTabList;             /* List of tables in the join */
  int iTop;                      /* The very beginning of the WHERE loop */
  int iContinue;                 /* Jump here to continue with next record */
  int iBreak;                    /* Jump here to break out of the loop */
  int nLevel;                    /* Number of nested loop */
  struct WhereClause *pWC;       /* Decomposition of the WHERE clause */
  sqlite3_index_info **apInfo;   /* Array of pointers to index info objects */
  WhereLevel a[1];               /* Information about each nest loop in WHERE */
};

/*
** A NameContext defines a context in which to resolve table and column
** names.  The context consists of a list of tables (the pSrcList) field and
** a list of named expression (pEList).  The named expression list may
................................................................................
int sqlite3IsReadOnly(Parse*, Table*, int);
void sqlite3OpenTable(Parse*, int iCur, int iDb, Table*, int);
#if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) && !defined(SQLITE_OMIT_SUBQUERY)
Expr *sqlite3LimitWhere(Parse *, SrcList *, Expr *, ExprList *, Expr *, Expr *, char *);
#endif
void sqlite3DeleteFrom(Parse*, SrcList*, Expr*);
void sqlite3Update(Parse*, SrcList*, ExprList*, Expr*, int);
WhereInfo *sqlite3WhereBegin(Parse*, SrcList*, Expr*, ExprList**, u8);
void sqlite3WhereEnd(WhereInfo*);
int sqlite3ExprCodeGetColumn(Parse*, Table*, int, int, int, int);
void sqlite3ExprCodeMove(Parse*, int, int, int);
void sqlite3ExprCodeCopy(Parse*, int, int, int);
void sqlite3ExprClearColumnCache(Parse*, int);
void sqlite3ExprCacheAffinityChange(Parse*, int, int);
int sqlite3ExprWritableRegister(Parse*,int,int);

**    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.
**
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.815 2008/12/23 23:56:22 drh Exp $
*/
#ifndef _SQLITEINT_H_
#define _SQLITEINT_H_

/*
** Include the configuration header output by 'configure' if we're using the
** autoconf-based build
................................................................................
  */
  sqlite3_index_info *pIdxInfo;  /* Index info for n-th source table */
};

/*
** Flags appropriate for the wctrlFlags parameter of sqlite3WhereBegin().
*/
#define WHERE_ORDERBY_NORMAL    0x000  /* No-op */
#define WHERE_ORDERBY_MIN       0x001  /* ORDER BY processing for min() func */
#define WHERE_ORDERBY_MAX       0x002  /* ORDER BY processing for max() func */
#define WHERE_ONEPASS_DESIRED   0x004  /* Want to do one-pass UPDATE/DELETE */
#define WHERE_FILL_ROWSET       0x008  /* Save results in a RowSet object */

/*
** The WHERE clause processing routine has two halves.  The
** first part does the start of the WHERE loop and the second
** half does the tail of the WHERE loop.  An instance of
** this structure is returned by the first half and passed
** into the second half to give some continuity.
*/
struct WhereInfo {
  Parse *pParse;       /* Parsing and code generating context */
  u8 okOnePass;        /* Ok to use one-pass algorithm for UPDATE or DELETE */
  int regRowSet;                 /* Store rowids in this rowset if >=0 */
  SrcList *pTabList;             /* List of tables in the join */
  int iTop;                      /* The very beginning of the WHERE loop */
  int iContinue;                 /* Jump here to continue with next record */
  int iBreak;                    /* Jump here to break out of the loop */
  int nLevel;                    /* Number of nested loop */
  struct WhereClause *pWC;       /* Decomposition of the WHERE clause */

  WhereLevel a[1];               /* Information about each nest loop in WHERE */
};

/*
** A NameContext defines a context in which to resolve table and column
** names.  The context consists of a list of tables (the pSrcList) field and
** a list of named expression (pEList).  The named expression list may
................................................................................
int sqlite3IsReadOnly(Parse*, Table*, int);
void sqlite3OpenTable(Parse*, int iCur, int iDb, Table*, int);
#if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) && !defined(SQLITE_OMIT_SUBQUERY)
Expr *sqlite3LimitWhere(Parse *, SrcList *, Expr *, ExprList *, Expr *, Expr *, char *);
#endif
void sqlite3DeleteFrom(Parse*, SrcList*, Expr*);
void sqlite3Update(Parse*, SrcList*, ExprList*, Expr*, int);
WhereInfo *sqlite3WhereBegin(Parse*, SrcList*, Expr*, ExprList**, u8, int);
void sqlite3WhereEnd(WhereInfo*);
int sqlite3ExprCodeGetColumn(Parse*, Table*, int, int, int, int);
void sqlite3ExprCodeMove(Parse*, int, int, int);
void sqlite3ExprCodeCopy(Parse*, int, int, int);
void sqlite3ExprClearColumnCache(Parse*, int);
void sqlite3ExprCacheAffinityChange(Parse*, int, int);
int sqlite3ExprWritableRegister(Parse*,int,int);

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code routines that are called by the parser
** to handle UPDATE statements.
**
** $Id: update.c,v 1.190 2008/12/10 22:15:00 drh Exp $
*/
#include "sqliteInt.h"

#ifndef SQLITE_OMIT_VIRTUALTABLE
/* Forward declaration */
static void updateVirtualTable(
  Parse *pParse,       /* The parsing context */
................................................................................
    goto update_cleanup;
  }

  /* Begin the database scan
  */
  sqlite3VdbeAddOp2(v, OP_Null, 0, regOldRowid);
  pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, 0,
                             WHERE_ONEPASS_DESIRED);
  if( pWInfo==0 ) goto update_cleanup;
  okOnePass = pWInfo->okOnePass;

  /* Remember the rowid of every item to be updated.
  */
  sqlite3VdbeAddOp2(v, IsVirtual(pTab)?OP_VRowid:OP_Rowid, iCur, regOldRowid);
  if( !okOnePass ){

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code routines that are called by the parser
** to handle UPDATE statements.
**
** $Id: update.c,v 1.191 2008/12/23 23:56:22 drh Exp $
*/
#include "sqliteInt.h"

#ifndef SQLITE_OMIT_VIRTUALTABLE
/* Forward declaration */
static void updateVirtualTable(
  Parse *pParse,       /* The parsing context */
................................................................................
    goto update_cleanup;
  }

  /* Begin the database scan
  */
  sqlite3VdbeAddOp2(v, OP_Null, 0, regOldRowid);
  pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, 0,
                             WHERE_ONEPASS_DESIRED, 0);
  if( pWInfo==0 ) goto update_cleanup;
  okOnePass = pWInfo->okOnePass;

  /* Remember the rowid of every item to be updated.
  */
  sqlite3VdbeAddOp2(v, IsVirtual(pTab)?OP_VRowid:OP_Rowid, iCur, regOldRowid);
  if( !okOnePass ){

** This module contains C code that generates VDBE code used to process
** the WHERE clause of SQL statements.  This module is responsible for
** 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".
**
** $Id: where.c,v 1.342 2008/12/23 16:23:05 drh Exp $
*/
#include "sqliteInt.h"

/*
** Trace output macros
*/
#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
................................................................................
    if( cost<pCost->rCost ){
      pCost->rCost = cost;
      pCost->nRow = nRow;
      pCost->plan.wsFlags = wsFlags;
    }
  }

#if SQLITE_ENABLE_MULTI_OR
  /* Search for an OR-clause that can be used to look up the table.
  */
  maskSrc = getMask(pWC->pMaskSet, iCur);
  for(i=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
    WhereClause tempWC;
    tempWC = *pWC;
    tempWC.nSlot = 1;
................................................................................
        pCost->rCost = rTotal;
        pCost->nRow = nRow;
        pCost->plan.wsFlags = WHERE_MULTI_OR;
        pCost->plan.u.pTerm = pTerm;
      }
    }
  }
#endif

  /* If the pSrc table is the right table of a LEFT JOIN then we may not
  ** use an index to satisfy IS NULL constraints on that table.  This is
  ** because columns might end up being NULL if the table does not match -
  ** a circumstance which the index cannot help us discover.  Ticket #2177.
  */
  if( (pSrc->jointype & JT_LEFT)!=0 ){
................................................................................
    testcase( pTerm->eOperator & WO_IN );
    if( (pTerm->eOperator & (WO_ISNULL|WO_IN))==0 ){
      sqlite3VdbeAddOp2(v, OP_IsNull, regBase+j, pLevel->addrBrk);
    }
  }
  return regBase;
}




















/*
** 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 bRev;            /* True if we need to scan in reverse order */
  WhereLevel *pLevel;  /* The where level to be coded */
  WhereClause *pWC;    /* Decomposition of the entire WHERE clause */
  WhereTerm *pTerm;               /* A WHERE clause term */
  Parse *pParse;                  /* Parsing context */
  Vdbe *v;                        /* The prepared stmt under constructions */
  struct SrcList_item *pTabItem;  /* FROM clause term being coded */
  int addrBrk;
  int addrCont;


  

  pParse = pWInfo->pParse;
  v = pParse->pVdbe;
  pWC = pWInfo->pWC;
  pLevel = &pWInfo->a[iLevel];
  pTabItem = &pWInfo->pTabList->a[pLevel->iFrom];
  iCur = pTabItem->iCursor;
  bRev = (pLevel->plan.wsFlags & WHERE_REVERSE)!=0;
  omitTable = (pLevel->plan.wsFlags & WHERE_IDX_ONLY)!=0;



  /* 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
................................................................................
    }
    assert( pParse->disableColCache );
    pParse->disableColCache--;
    sqlite3VdbeAddOp2(v, OP_Integer, pVtabIdx->idxNum, iReg);
    sqlite3VdbeAddOp2(v, OP_Integer, j-1, iReg+1);
    sqlite3VdbeAddOp4(v, OP_VFilter, iCur, addrBrk, iReg, pVtabIdx->idxStr,
                      pVtabIdx->needToFreeIdxStr ? P4_MPRINTF : P4_STATIC);
    sqlite3ReleaseTempRange(pParse, iReg, nConstraint+2);
    pVtabIdx->needToFreeIdxStr = 0;
    for(j=0; j<nConstraint; j++){
      if( aUsage[j].omit ){
        int iTerm = aConstraint[j].iTermOffset;
        disableTerm(pLevel, &pWC->a[iTerm]);
      }
    }
    pLevel->op = OP_VNext;
    pLevel->p1 = iCur;
    pLevel->p2 = sqlite3VdbeCurrentAddr(v);






  }else
#endif /* SQLITE_OMIT_VIRTUALTABLE */

  if( pLevel->plan.wsFlags & WHERE_ROWID_EQ ){
    /* Case 1:  We can directly reference a single row using an
    **          equality comparison against the ROWID field.  Or
    **          we reference multiple rows using a "rowid IN (...)"
................................................................................
    assert( pTerm->pExpr!=0 );
    assert( pTerm->leftCursor==iCur );
    assert( omitTable==0 );
    r1 = codeEqualityTerm(pParse, pTerm, pLevel, rtmp);
    addrNxt = pLevel->addrNxt;
    sqlite3VdbeAddOp2(v, OP_MustBeInt, r1, addrNxt);
    sqlite3VdbeAddOp3(v, OP_NotExists, iCur, addrNxt, r1);




    sqlite3ReleaseTempReg(pParse, rtmp);
    VdbeComment((v, "pk"));
    pLevel->op = OP_Noop;
  }else if( pLevel->plan.wsFlags & WHERE_ROWID_RANGE ){
    /* Case 2:  We have an inequality comparison against the ROWID field.
    */
    int testOp = OP_Noop;
................................................................................
      }
      disableTerm(pLevel, pEnd);
    }
    start = sqlite3VdbeCurrentAddr(v);
    pLevel->op = bRev ? OP_Prev : OP_Next;
    pLevel->p1 = iCur;
    pLevel->p2 = start;

    if( testOp!=OP_Noop ){
      int r1 = sqlite3GetTempReg(pParse);
      sqlite3VdbeAddOp2(v, OP_Rowid, iCur, r1);

      sqlite3VdbeAddOp3(v, testOp, memEndValue, addrBrk, r1);
      sqlite3VdbeChangeP5(v, SQLITE_AFF_NUMERIC | SQLITE_JUMPIFNULL);




      sqlite3ReleaseTempReg(pParse, r1);
    }
  }else if( pLevel->plan.wsFlags & (WHERE_COLUMN_RANGE|WHERE_COLUMN_EQ) ){
    /* Case 3: A scan using an index.
    **
    **         The WHERE clause may contain zero or more equality 
    **         terms ("==" or "IN" operators) that refer to the N
................................................................................
    testcase( pLevel->plan.wsFlags & WHERE_TOP_LIMIT );
    if( pLevel->plan.wsFlags & (WHERE_BTM_LIMIT|WHERE_TOP_LIMIT) ){
      sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, nEq, r1);
      sqlite3VdbeAddOp2(v, OP_IsNull, r1, addrCont);
    }

    /* Seek the table cursor, if required */



    if( !omitTable ){
      sqlite3VdbeAddOp2(v, OP_IdxRowid, iIdxCur, r1);



      sqlite3VdbeAddOp2(v, OP_Seek, iCur, r1);  /* Deferred seek */

    }
    sqlite3ReleaseTempReg(pParse, r1);

    /* Record the instruction used to terminate the loop. Disable 
    ** WHERE clause terms made redundant by the index range scan.
    */
    pLevel->op = bRev ? OP_Prev : OP_Next;
    pLevel->p1 = iIdxCur;
    disableTerm(pLevel, pRangeStart);
    disableTerm(pLevel, pRangeEnd);
  }else

#if SQLITE_ENABLE_MULTI_OR

  if( pLevel->plan.wsFlags & WHERE_MULTI_OR ){
    /* Case 4:  Two or more separately indexed terms connected by OR
    **
    ** Example:
    **
    **   CREATE TABLE t1(a,b,c,d);
    **   CREATE INDEX i1 ON t1(a);
................................................................................
    **        Seek       i, 2
    **
    ** The bottom of the loop looks like this:
    **
    **        Goto       0, A
    **     B:
    */
    int regRowset;         /* Register holding the RowSet object */
    int regNextRowid;      /* Register holding next rowid */
    WhereTerm *pTerm;      /* The complete OR-clause */
    WhereClause *pOrWc;    /* The OR-clause broken out into subterms */
    WhereTerm *pOrTerm;    /* A single subterm within the OR-clause */
    SrcList oneTab;        /* Shortened table list */
   
    pTerm = pLevel->plan.u.pTerm;
    assert( pTerm!=0 );
    assert( pTerm->eOperator==WO_OR );
    assert( (pTerm->wtFlags & TERM_ORINFO)!=0 );
    pOrWc = &pTerm->u.pOrInfo->wc;

    



    regRowset = sqlite3GetTempReg(pParse);
    regNextRowid = sqlite3GetTempReg(pParse);
    sqlite3VdbeAddOp2(v, OP_Null, 0, regRowset);

    oneTab.nSrc = 1;
    oneTab.nAlloc = 1;
    oneTab.a[0] = *pTabItem;
    for(j=0, pOrTerm=pOrWc->a; j<pOrWc->nTerm; j++, pOrTerm++){
      WhereInfo *pSubWInfo;
      if( pOrTerm->leftCursor!=iCur ) continue;
      pSubWInfo = sqlite3WhereBegin(pParse, &oneTab, pOrTerm->pExpr, 0, 0);

      if( pSubWInfo ){
        sqlite3VdbeAddOp2(v, OP_Rowid, oneTab.a[0].iCursor, regNextRowid);
        sqlite3VdbeAddOp2(v, OP_RowSetAdd, regRowset, regNextRowid);
        pSubWInfo->a[0].plan.wsFlags |= WHERE_IDX_ONLY;
        sqlite3WhereEnd(pSubWInfo);
      }
    }
    sqlite3VdbeResolveLabel(v, addrCont);


    addrCont = 
       sqlite3VdbeAddOp3(v, OP_RowSetRead, regRowset, addrBrk, regNextRowid);
    sqlite3VdbeAddOp2(v, OP_Seek, iCur, regNextRowid);
    sqlite3ReleaseTempReg(pParse, regNextRowid);

    pLevel->op = OP_Goto;
    pLevel->p2 = addrCont;


  }else
#endif /* SQLITE_ENABLE_MULTI_OR */

  {
    /* Case 5:  There is no usable index.  We must do a complete
    **          scan of the entire table.
    */
    assert( omitTable==0 );
    assert( bRev==0 );
    pLevel->op = OP_Next;
    pLevel->p1 = iCur;
    pLevel->p2 = 1 + sqlite3VdbeAddOp2(v, OP_Rewind, iCur, addrBrk);
    pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;

  }
  notReady &= ~getMask(pWC->pMaskSet, iCur);

  /* Insert code to test every subexpression that can be completely
  ** computed using the current set of tables.
  */
  k = 0;
................................................................................
      if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
      if( (pTerm->prereqAll & notReady)!=0 ) continue;
      assert( pTerm->pExpr );
      sqlite3ExprIfFalse(pParse, pTerm->pExpr, addrCont, SQLITE_JUMPIFNULL);
      pTerm->wtFlags |= TERM_CODED;
    }
  }



















  return notReady;
}

#if defined(SQLITE_TEST)
/*
** The following variable holds a text description of query plan generated
** by the most recent call to sqlite3WhereBegin().  Each call to WhereBegin
................................................................................
** output order, then the *ppOrderBy is unchanged.
*/
WhereInfo *sqlite3WhereBegin(
  Parse *pParse,        /* The parser context */
  SrcList *pTabList,    /* A list of all tables to be scanned */
  Expr *pWhere,         /* The WHERE clause */
  ExprList **ppOrderBy, /* An ORDER BY clause, or NULL */
  u8 wctrlFlags         /* One of the WHERE_* flags defined in sqliteInt.h */

){
  int i;                     /* Loop counter */
  WhereInfo *pWInfo;         /* Will become the return value of this function */
  Vdbe *v = pParse->pVdbe;   /* The virtual database engine */
  Bitmask notReady;          /* Cursors that are not yet positioned */
  WhereMaskSet *pMaskSet;    /* The expression mask set */
  //WhereClause wc;          /* The WHERE clause is divided into these terms */
................................................................................
  if( db->mallocFailed ){
    goto whereBeginError;
  }
  pWInfo->nLevel = pTabList->nSrc;
  pWInfo->pParse = pParse;
  pWInfo->pTabList = pTabList;
  pWInfo->iBreak = sqlite3VdbeMakeLabel(v);

  pWInfo->pWC = pWC = (WhereClause*)&pWInfo->a[pWInfo->nLevel];
  pMaskSet = (WhereMaskSet*)&pWC[1];

  /* Split the WHERE clause into separate subexpressions where each
  ** subexpression is separated by an AND operator.
  */
  initMaskSet(pMaskSet);

** This module contains C code that generates VDBE code used to process
** the WHERE clause of SQL statements.  This module is responsible for
** 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".
**
** $Id: where.c,v 1.343 2008/12/23 23:56:22 drh Exp $
*/
#include "sqliteInt.h"

/*
** Trace output macros
*/
#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
................................................................................
    if( cost<pCost->rCost ){
      pCost->rCost = cost;
      pCost->nRow = nRow;
      pCost->plan.wsFlags = wsFlags;
    }
  }

#ifndef SQLITE_OMIT_OR_OPTIMIZATION
  /* Search for an OR-clause that can be used to look up the table.
  */
  maskSrc = getMask(pWC->pMaskSet, iCur);
  for(i=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
    WhereClause tempWC;
    tempWC = *pWC;
    tempWC.nSlot = 1;
................................................................................
        pCost->rCost = rTotal;
        pCost->nRow = nRow;
        pCost->plan.wsFlags = WHERE_MULTI_OR;
        pCost->plan.u.pTerm = pTerm;
      }
    }
  }
#endif /* SQLITE_OMIT_OR_OPTIMIZATION */

  /* If the pSrc table is the right table of a LEFT JOIN then we may not
  ** use an index to satisfy IS NULL constraints on that table.  This is
  ** because columns might end up being NULL if the table does not match -
  ** a circumstance which the index cannot help us discover.  Ticket #2177.
  */
  if( (pSrc->jointype & JT_LEFT)!=0 ){
................................................................................
    testcase( pTerm->eOperator & WO_IN );
    if( (pTerm->eOperator & (WO_ISNULL|WO_IN))==0 ){
      sqlite3VdbeAddOp2(v, OP_IsNull, regBase+j, pLevel->addrBrk);
    }
  }
  return regBase;
}

/*
** Return TRUE if the WhereClause pWC contains no terms that
** are not virtual and which have not been coded.
**
** To put it another way, return TRUE if no additional WHERE clauses
** tests are required in order to establish that the current row
** should go to output and return FALSE if there are some terms of
** the WHERE clause that need to be validated before outputing the row.
*/
static int whereRowReadyForOutput(WhereClause *pWC){
  WhereTerm *pTerm;
  int j;
 
  for(pTerm=pWC->a, j=pWC->nTerm; j>0; j--, pTerm++){
    if( (pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED))==0 ) return 0;
  }
  return 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 bRev;            /* True if we need to scan in reverse order */
  WhereLevel *pLevel;  /* The where level to be coded */
  WhereClause *pWC;    /* Decomposition of the entire WHERE clause */
  WhereTerm *pTerm;               /* A WHERE clause term */
  Parse *pParse;                  /* Parsing context */
  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 regRowSet;       /* Write rowids to this RowSet if non-negative */
  int codeRowSetEarly; /* True if index fully constrains the search */
  

  pParse = pWInfo->pParse;
  v = pParse->pVdbe;
  pWC = pWInfo->pWC;
  pLevel = &pWInfo->a[iLevel];
  pTabItem = &pWInfo->pTabList->a[pLevel->iFrom];
  iCur = pTabItem->iCursor;
  bRev = (pLevel->plan.wsFlags & WHERE_REVERSE)!=0;
  omitTable = (pLevel->plan.wsFlags & WHERE_IDX_ONLY)!=0;
  regRowSet = pWInfo->regRowSet;
  codeRowSetEarly = 0;

  /* 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
................................................................................
    }
    assert( pParse->disableColCache );
    pParse->disableColCache--;
    sqlite3VdbeAddOp2(v, OP_Integer, pVtabIdx->idxNum, iReg);
    sqlite3VdbeAddOp2(v, OP_Integer, j-1, iReg+1);
    sqlite3VdbeAddOp4(v, OP_VFilter, iCur, addrBrk, iReg, pVtabIdx->idxStr,
                      pVtabIdx->needToFreeIdxStr ? P4_MPRINTF : P4_STATIC);

    pVtabIdx->needToFreeIdxStr = 0;
    for(j=0; j<nConstraint; j++){
      if( aUsage[j].omit ){
        int iTerm = aConstraint[j].iTermOffset;
        disableTerm(pLevel, &pWC->a[iTerm]);
      }
    }
    pLevel->op = OP_VNext;
    pLevel->p1 = iCur;
    pLevel->p2 = sqlite3VdbeCurrentAddr(v);
    codeRowSetEarly = regRowSet>=0 ? whereRowReadyForOutput(pWC) : 0;
    if( codeRowSetEarly ){
      sqlite3VdbeAddOp2(v, OP_VRowid, iCur, iReg);
      sqlite3VdbeAddOp2(v, OP_RowSetAdd, regRowSet, iReg);
    }
    sqlite3ReleaseTempRange(pParse, iReg, nConstraint+2);
  }else
#endif /* SQLITE_OMIT_VIRTUALTABLE */

  if( pLevel->plan.wsFlags & WHERE_ROWID_EQ ){
    /* Case 1:  We can directly reference a single row using an
    **          equality comparison against the ROWID field.  Or
    **          we reference multiple rows using a "rowid IN (...)"
................................................................................
    assert( pTerm->pExpr!=0 );
    assert( pTerm->leftCursor==iCur );
    assert( omitTable==0 );
    r1 = codeEqualityTerm(pParse, pTerm, pLevel, rtmp);
    addrNxt = pLevel->addrNxt;
    sqlite3VdbeAddOp2(v, OP_MustBeInt, r1, addrNxt);
    sqlite3VdbeAddOp3(v, OP_NotExists, iCur, addrNxt, r1);
    codeRowSetEarly = (pWC->nTerm==1 && regRowSet>=0) ?1:0;
    if( codeRowSetEarly ){
      sqlite3VdbeAddOp2(v, OP_RowSetAdd, regRowSet, r1);
    }
    sqlite3ReleaseTempReg(pParse, rtmp);
    VdbeComment((v, "pk"));
    pLevel->op = OP_Noop;
  }else if( pLevel->plan.wsFlags & WHERE_ROWID_RANGE ){
    /* Case 2:  We have an inequality comparison against the ROWID field.
    */
    int testOp = OP_Noop;
................................................................................
      }
      disableTerm(pLevel, pEnd);
    }
    start = sqlite3VdbeCurrentAddr(v);
    pLevel->op = bRev ? OP_Prev : OP_Next;
    pLevel->p1 = iCur;
    pLevel->p2 = start;
    codeRowSetEarly = regRowSet>=0 ? whereRowReadyForOutput(pWC) : 0;
    if( codeRowSetEarly || testOp!=OP_Noop ){
      int r1 = sqlite3GetTempReg(pParse);
      sqlite3VdbeAddOp2(v, OP_Rowid, iCur, r1);
      if( testOp!=OP_Noop ){
        sqlite3VdbeAddOp3(v, testOp, memEndValue, addrBrk, r1);
        sqlite3VdbeChangeP5(v, SQLITE_AFF_NUMERIC | SQLITE_JUMPIFNULL);
      }
      if( codeRowSetEarly ){
        sqlite3VdbeAddOp2(v, OP_RowSetAdd, regRowSet, r1);
      }
      sqlite3ReleaseTempReg(pParse, r1);
    }
  }else if( pLevel->plan.wsFlags & (WHERE_COLUMN_RANGE|WHERE_COLUMN_EQ) ){
    /* Case 3: A scan using an index.
    **
    **         The WHERE clause may contain zero or more equality 
    **         terms ("==" or "IN" operators) that refer to the N
................................................................................
    testcase( pLevel->plan.wsFlags & WHERE_TOP_LIMIT );
    if( pLevel->plan.wsFlags & (WHERE_BTM_LIMIT|WHERE_TOP_LIMIT) ){
      sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, nEq, r1);
      sqlite3VdbeAddOp2(v, OP_IsNull, r1, addrCont);
    }

    /* Seek the table cursor, if required */
    disableTerm(pLevel, pRangeStart);
    disableTerm(pLevel, pRangeEnd);
    codeRowSetEarly = regRowSet>=0 ? whereRowReadyForOutput(pWC) : 0;
    if( !omitTable || codeRowSetEarly ){
      sqlite3VdbeAddOp2(v, OP_IdxRowid, iIdxCur, r1);
      if( codeRowSetEarly ){
        sqlite3VdbeAddOp2(v, OP_RowSetAdd, regRowSet, r1);
      }else{
        sqlite3VdbeAddOp2(v, OP_Seek, iCur, r1);  /* Deferred seek */
      }
    }
    sqlite3ReleaseTempReg(pParse, r1);

    /* Record the instruction used to terminate the loop. Disable 
    ** WHERE clause terms made redundant by the index range scan.
    */
    pLevel->op = bRev ? OP_Prev : OP_Next;
    pLevel->p1 = iIdxCur;


  }else


#ifndef SQLITE_OMIT_OR_OPTIMIZATION
  if( pLevel->plan.wsFlags & WHERE_MULTI_OR ){
    /* Case 4:  Two or more separately indexed terms connected by OR
    **
    ** Example:
    **
    **   CREATE TABLE t1(a,b,c,d);
    **   CREATE INDEX i1 ON t1(a);
................................................................................
    **        Seek       i, 2
    **
    ** The bottom of the loop looks like this:
    **
    **        Goto       0, A
    **     B:
    */
    int regOrRowset;       /* Register holding the RowSet object */
    int regNextRowid;      /* Register holding next rowid */
    WhereTerm *pTerm;      /* The complete OR-clause */
    WhereClause *pOrWc;    /* The OR-clause broken out into subterms */
    WhereTerm *pOrTerm;    /* A single subterm within the OR-clause */
    SrcList oneTab;        /* Shortened table list */
   
    pTerm = pLevel->plan.u.pTerm;
    assert( pTerm!=0 );
    assert( pTerm->eOperator==WO_OR );
    assert( (pTerm->wtFlags & TERM_ORINFO)!=0 );
    pOrWc = &pTerm->u.pOrInfo->wc;
    codeRowSetEarly = (regRowSet>=0 && pWC->nTerm==1) ?1:0;

    if( codeRowSetEarly ){
      regOrRowset = regRowSet;
    }else{
      regOrRowset = sqlite3GetTempReg(pParse);

      sqlite3VdbeAddOp2(v, OP_Null, 0, regOrRowset);
    }
    oneTab.nSrc = 1;
    oneTab.nAlloc = 1;
    oneTab.a[0] = *pTabItem;
    for(j=0, pOrTerm=pOrWc->a; j<pOrWc->nTerm; j++, pOrTerm++){
      WhereInfo *pSubWInfo;
      if( pOrTerm->leftCursor!=iCur ) continue;
      pSubWInfo = sqlite3WhereBegin(pParse, &oneTab, pOrTerm->pExpr, 0,
                        WHERE_FILL_ROWSET, regOrRowset);
      if( pSubWInfo ){


        pSubWInfo->a[0].plan.wsFlags |= WHERE_IDX_ONLY;
        sqlite3WhereEnd(pSubWInfo);
      }
    }
    sqlite3VdbeResolveLabel(v, addrCont);
    if( !codeRowSetEarly ){
      regNextRowid = sqlite3GetTempReg(pParse);
      addrCont = 
         sqlite3VdbeAddOp3(v, OP_RowSetRead, regOrRowset,addrBrk,regNextRowid);
      sqlite3VdbeAddOp2(v, OP_Seek, iCur, regNextRowid);
      sqlite3ReleaseTempReg(pParse, regNextRowid);
      /* sqlite3ReleaseTempReg(pParse, regOrRowset); // Preserve the RowSet */
      pLevel->op = OP_Goto;
      pLevel->p2 = addrCont;
    }
    disableTerm(pLevel, pTerm);
  }else
#endif /* SQLITE_OMIT_OR_OPTIMIZATION */

  {
    /* Case 5:  There is no usable index.  We must do a complete
    **          scan of the entire table.
    */
    assert( omitTable==0 );
    assert( bRev==0 );
    pLevel->op = OP_Next;
    pLevel->p1 = iCur;
    pLevel->p2 = 1 + sqlite3VdbeAddOp2(v, OP_Rewind, iCur, addrBrk);
    pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
    codeRowSetEarly = 0;
  }
  notReady &= ~getMask(pWC->pMaskSet, iCur);

  /* Insert code to test every subexpression that can be completely
  ** computed using the current set of tables.
  */
  k = 0;
................................................................................
      if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
      if( (pTerm->prereqAll & notReady)!=0 ) continue;
      assert( pTerm->pExpr );
      sqlite3ExprIfFalse(pParse, pTerm->pExpr, addrCont, SQLITE_JUMPIFNULL);
      pTerm->wtFlags |= TERM_CODED;
    }
  }

  /*
  ** If it was requested to store the results in a rowset and that has
  ** not already been do, then do so now.
  */
  if( regRowSet>=0 && !codeRowSetEarly ){
    int r1 = sqlite3GetTempReg(pParse);
#ifndef SQLITE_OMIT_VIRTUALTABLE
    if(  (pLevel->plan.wsFlags & WHERE_VIRTUALTABLE)!=0 ){
      sqlite3VdbeAddOp2(v, OP_VRowid, iCur, r1);
    }else
#endif
    {
      sqlite3VdbeAddOp2(v, OP_Rowid, iCur, r1);
    }
    sqlite3VdbeAddOp2(v, OP_RowSetAdd, regRowSet, r1);
    sqlite3ReleaseTempReg(pParse, r1);
  }

  return notReady;
}

#if defined(SQLITE_TEST)
/*
** The following variable holds a text description of query plan generated
** by the most recent call to sqlite3WhereBegin().  Each call to WhereBegin
................................................................................
** output order, then the *ppOrderBy is unchanged.
*/
WhereInfo *sqlite3WhereBegin(
  Parse *pParse,        /* The parser context */
  SrcList *pTabList,    /* A list of all tables to be scanned */
  Expr *pWhere,         /* The WHERE clause */
  ExprList **ppOrderBy, /* An ORDER BY clause, or NULL */
  u8 wctrlFlags,        /* One of the WHERE_* flags defined in sqliteInt.h */
  int regRowSet         /* Register hold RowSet if WHERE_FILL_ROWSET is set */
){
  int i;                     /* Loop counter */
  WhereInfo *pWInfo;         /* Will become the return value of this function */
  Vdbe *v = pParse->pVdbe;   /* The virtual database engine */
  Bitmask notReady;          /* Cursors that are not yet positioned */
  WhereMaskSet *pMaskSet;    /* The expression mask set */
  //WhereClause wc;          /* The WHERE clause is divided into these terms */
................................................................................
  if( db->mallocFailed ){
    goto whereBeginError;
  }
  pWInfo->nLevel = pTabList->nSrc;
  pWInfo->pParse = pParse;
  pWInfo->pTabList = pTabList;
  pWInfo->iBreak = sqlite3VdbeMakeLabel(v);
  pWInfo->regRowSet = (wctrlFlags & WHERE_FILL_ROWSET) ? regRowSet : -1;
  pWInfo->pWC = pWC = (WhereClause*)&pWInfo->a[pWInfo->nLevel];
  pMaskSet = (WhereMaskSet*)&pWC[1];

  /* Split the WHERE clause into separate subexpressions where each
  ** subexpression is separated by an AND operator.
  */
  initMaskSet(pMaskSet);

# 2008 December 23
#
# 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 file implements regression tests for SQLite library.  The
# focus of this file is testing the multi-index OR clause optimizer.
#
# $Id: where7.test,v 1.1 2008/12/23 23:56:22 drh Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl

ifcapable !or_opt {
  finish_test
  return
}

# Evaluate SQL.  Return the result set followed by the
# and the number of full-scan steps.
#
proc count_steps {sql} {
  set r [db eval $sql]
  lappend r scan [db status step]
}

# Build some test data
#
do_test where7-1.1 {
  execsql {
    CREATE TABLE t1(a INTEGER PRIMARY KEY,b,c,d);
    INSERT INTO t1 VALUES(1,2,3,4);
    INSERT INTO t1 VALUES(2,3,4,5);
    INSERT INTO t1 VALUES(3,4,6,8);
    INSERT INTO t1 VALUES(4,5,10,15);
    INSERT INTO t1 VALUES(5,10,100,1000);
    CREATE INDEX t1b ON t1(b);
    CREATE INDEX t1c ON t1(c);
    SELECT * FROM t1;
  }
} {1 2 3 4 2 3 4 5 3 4 6 8 4 5 10 15 5 10 100 1000}
do_test where7-1.2 {
  count_steps {
    SELECT a FROM t1 WHERE b=3 OR c=6
  }
} {2 3 scan 0}
do_test where7-1.3 {
  count_steps {
    SELECT a FROM t1 WHERE b=3 OR +c=6
  }
} {2 3 scan 4}
do_test where7-1.4 {
  count_steps {
    SELECT a FROM t1 WHERE +b=3 OR c=6
  }
} {2 3 scan 4}
do_test where7-1.5 {
  count_steps {
    SELECT a FROM t1 WHERE 3=b OR c=6
  }
} {2 3 scan 0}
do_test where7-1.6 {
  count_steps {
    SELECT a FROM t1 WHERE (3=b OR c=6) AND +a>0
  }
} {2 3 scan 0}
do_test where7-1.7 {
  count_steps {
    SELECT a FROM t1 WHERE (b=3 OR c>10)
  }
} {2 5 scan 0}
do_test where7-1.8 {
  count_steps {
    SELECT a FROM t1 WHERE (b=3 OR c>=10)
  }
} {2 4 5 scan 0}
do_test where7-1.9 {
  count_steps {
    SELECT a FROM t1 WHERE (b=3 OR c>=10 OR c=4)
  }
} {2 4 5 scan 0}
do_test where7-1.10 {
  count_steps {
    SELECT a FROM t1 WHERE (b=3 OR c>=10 OR c=4 OR b>10)
  }
} {2 4 5 scan 0}


finish_test