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Overview
Comment:Do not reuse factored constants that might have had their encodings changed.
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SHA1: 487f20366ce77f0c90865d10d5aaedd95af98694
User & Date: drh 2013-11-21 21:23:31
Context
2013-11-21
21:40
Modify wordcount so that timer information appears on standard error instead of standard output. Rename the run-wordcount.bash script to run-wordcount.sh and simplify it so that it stands a better chance of running on non-GNU systems. check-in: 586c11ed user: drh tags: trunk
21:23
Do not reuse factored constants that might have had their encodings changed. check-in: 487f2036 user: drh tags: trunk
20:48
Fix the code generator to honor turning off constant expression factoring. check-in: 88262266 user: drh tags: trunk
Changes
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Changes to src/expr.c.

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  sqlite3ReleaseTempReg(pParse, regFree2);
  return inReg;
}

/*
** Factor out the code of the given expression to initialization time.
*/
void sqlite3ExprCodeAtInit(Parse *pParse, Expr *pExpr, int regDest){





  ExprList *p;
  assert( ConstFactorOk(pParse) );
  p = pParse->pConstExpr;
  pExpr = sqlite3ExprDup(pParse->db, pExpr, 0);
  p = sqlite3ExprListAppend(pParse, p, pExpr);


  if( p ) p->a[p->nExpr-1].u.iConstExprReg = regDest;


  pParse->pConstExpr = p;
}

/*
** Generate code to evaluate an expression and store the results
** into a register.  Return the register number where the results
** are stored.
................................................................................
   && pExpr->op!=TK_REGISTER
   && sqlite3ExprIsConstantNotJoin(pExpr)
  ){
    ExprList *p = pParse->pConstExpr;
    int i;
    *pReg  = 0;
    if( p ){
      for(i=0; i<p->nExpr; i++){
        if( sqlite3ExprCompare(p->a[i].pExpr, pExpr, -1)==0 ){

          return p->a[i].u.iConstExprReg;
        }
      }
    }
    r2 = ++pParse->nMem;
    sqlite3ExprCodeAtInit(pParse, pExpr, r2);
  }else{
    int r1 = sqlite3GetTempReg(pParse);
    r2 = sqlite3ExprCodeTarget(pParse, pExpr, r1);
    if( r2==r1 ){
      *pReg = r1;
    }else{
      sqlite3ReleaseTempReg(pParse, r1);
................................................................................
  assert( target>0 );
  assert( pParse->pVdbe!=0 );  /* Never gets this far otherwise */
  n = pList->nExpr;
  if( !ConstFactorOk(pParse) ) flags &= ~SQLITE_ECEL_FACTOR;
  for(pItem=pList->a, i=0; i<n; i++, pItem++){
    Expr *pExpr = pItem->pExpr;
    if( (flags & SQLITE_ECEL_FACTOR)!=0 && sqlite3ExprIsConstant(pExpr) ){
      sqlite3ExprCodeAtInit(pParse, pExpr, target+i);
    }else{
      int inReg = sqlite3ExprCodeTarget(pParse, pExpr, target+i);
      if( inReg!=target+i ){
        sqlite3VdbeAddOp2(pParse->pVdbe, copyOp, inReg, target+i);
      }
    }
  }







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  sqlite3ReleaseTempReg(pParse, regFree2);
  return inReg;
}

/*
** Factor out the code of the given expression to initialization time.
*/
void sqlite3ExprCodeAtInit(
  Parse *pParse,    /* Parsing context */
  Expr *pExpr,      /* The expression to code when the VDBE initializes */
  int regDest,      /* Store the value in this register */
  u8 reusable       /* True if this expression is reusable */
){
  ExprList *p;
  assert( ConstFactorOk(pParse) );
  p = pParse->pConstExpr;
  pExpr = sqlite3ExprDup(pParse->db, pExpr, 0);
  p = sqlite3ExprListAppend(pParse, p, pExpr);
  if( p ){
     struct ExprList_item *pItem = &p->a[p->nExpr-1];
     pItem->u.iConstExprReg = regDest;
     pItem->reusable = reusable;
  }
  pParse->pConstExpr = p;
}

/*
** Generate code to evaluate an expression and store the results
** into a register.  Return the register number where the results
** are stored.
................................................................................
   && pExpr->op!=TK_REGISTER
   && sqlite3ExprIsConstantNotJoin(pExpr)
  ){
    ExprList *p = pParse->pConstExpr;
    int i;
    *pReg  = 0;
    if( p ){
      struct ExprList_item *pItem;
      for(pItem=p->a, i=p->nExpr; i>0; pItem++, i--){
        if( pItem->reusable && sqlite3ExprCompare(pItem->pExpr,pExpr,-1)==0 ){
          return pItem->u.iConstExprReg;
        }
      }
    }
    r2 = ++pParse->nMem;
    sqlite3ExprCodeAtInit(pParse, pExpr, r2, 1);
  }else{
    int r1 = sqlite3GetTempReg(pParse);
    r2 = sqlite3ExprCodeTarget(pParse, pExpr, r1);
    if( r2==r1 ){
      *pReg = r1;
    }else{
      sqlite3ReleaseTempReg(pParse, r1);
................................................................................
  assert( target>0 );
  assert( pParse->pVdbe!=0 );  /* Never gets this far otherwise */
  n = pList->nExpr;
  if( !ConstFactorOk(pParse) ) flags &= ~SQLITE_ECEL_FACTOR;
  for(pItem=pList->a, i=0; i<n; i++, pItem++){
    Expr *pExpr = pItem->pExpr;
    if( (flags & SQLITE_ECEL_FACTOR)!=0 && sqlite3ExprIsConstant(pExpr) ){
      sqlite3ExprCodeAtInit(pParse, pExpr, target+i, 0);
    }else{
      int inReg = sqlite3ExprCodeTarget(pParse, pExpr, target+i);
      if( inReg!=target+i ){
        sqlite3VdbeAddOp2(pParse->pVdbe, copyOp, inReg, target+i);
      }
    }
  }

Changes to src/sqliteInt.h.

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  struct ExprList_item { /* For each expression in the list */
    Expr *pExpr;            /* The list of expressions */
    char *zName;            /* Token associated with this expression */
    char *zSpan;            /* Original text of the expression */
    u8 sortOrder;           /* 1 for DESC or 0 for ASC */
    unsigned done :1;       /* A flag to indicate when processing is finished */
    unsigned bSpanIsTab :1; /* zSpan holds DB.TABLE.COLUMN */

    union {
      struct {
        u16 iOrderByCol;      /* For ORDER BY, column number in result set */
        u16 iAlias;           /* Index into Parse.aAlias[] for zName */
      } x;
      int iConstExprReg;      /* Register in which Expr value is cached */
    } u;
................................................................................
void sqlite3ExprCacheStore(Parse*, int, int, int);
void sqlite3ExprCachePush(Parse*);
void sqlite3ExprCachePop(Parse*, int);
void sqlite3ExprCacheRemove(Parse*, int, int);
void sqlite3ExprCacheClear(Parse*);
void sqlite3ExprCacheAffinityChange(Parse*, int, int);
int sqlite3ExprCode(Parse*, Expr*, int);
void sqlite3ExprCodeAtInit(Parse*, Expr*, int);
int sqlite3ExprCodeTemp(Parse*, Expr*, int*);
int sqlite3ExprCodeTarget(Parse*, Expr*, int);
int sqlite3ExprCodeAndCache(Parse*, Expr*, int);
int sqlite3ExprCodeExprList(Parse*, ExprList*, int, u8);
#define SQLITE_ECEL_DUP      0x01  /* Deep, not shallow copies */
#define SQLITE_ECEL_FACTOR   0x02  /* Factor out constant terms */
void sqlite3ExprIfTrue(Parse*, Expr*, int, int);







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  struct ExprList_item { /* For each expression in the list */
    Expr *pExpr;            /* The list of expressions */
    char *zName;            /* Token associated with this expression */
    char *zSpan;            /* Original text of the expression */
    u8 sortOrder;           /* 1 for DESC or 0 for ASC */
    unsigned done :1;       /* A flag to indicate when processing is finished */
    unsigned bSpanIsTab :1; /* zSpan holds DB.TABLE.COLUMN */
    unsigned reusable :1;   /* Constant expression is reusable */
    union {
      struct {
        u16 iOrderByCol;      /* For ORDER BY, column number in result set */
        u16 iAlias;           /* Index into Parse.aAlias[] for zName */
      } x;
      int iConstExprReg;      /* Register in which Expr value is cached */
    } u;
................................................................................
void sqlite3ExprCacheStore(Parse*, int, int, int);
void sqlite3ExprCachePush(Parse*);
void sqlite3ExprCachePop(Parse*, int);
void sqlite3ExprCacheRemove(Parse*, int, int);
void sqlite3ExprCacheClear(Parse*);
void sqlite3ExprCacheAffinityChange(Parse*, int, int);
int sqlite3ExprCode(Parse*, Expr*, int);
void sqlite3ExprCodeAtInit(Parse*, Expr*, int, u8);
int sqlite3ExprCodeTemp(Parse*, Expr*, int*);
int sqlite3ExprCodeTarget(Parse*, Expr*, int);
int sqlite3ExprCodeAndCache(Parse*, Expr*, int);
int sqlite3ExprCodeExprList(Parse*, ExprList*, int, u8);
#define SQLITE_ECEL_DUP      0x01  /* Deep, not shallow copies */
#define SQLITE_ECEL_FACTOR   0x02  /* Factor out constant terms */
void sqlite3ExprIfTrue(Parse*, Expr*, int, int);

Added test/func5.test.



































































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# 2013-11-21
#
# 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.
#
#*************************************************************************
#
# Verify that constant string expressions that get factored into initializing
# code are not reused between function parameters and other values in the
# VDBE program, as the function might have changed the encoding.
#
set testdir [file dirname $argv0]
source $testdir/tester.tcl

do_execsql_test func5-1.1 {
  PRAGMA encoding=UTF16le;
  CREATE TABLE t1(x,a,b,c);
  INSERT INTO t1 VALUES(1,'ab','cd',1);
  INSERT INTO t1 VALUES(2,'gh','ef',5);
  INSERT INTO t1 VALUES(3,'pqr','fuzzy',99);
  INSERT INTO t1 VALUES(4,'abcdefg','xy',22);
  INSERT INTO t1 VALUES(5,'shoe','mayer',2953);
  SELECT x FROM t1 WHERE c=instr('abcdefg',b) OR a='abcdefg' ORDER BY +x;
} {2 4}
do_execsql_test func5-1.2 {
  SELECT x FROM t1 WHERE a='abcdefg' OR c=instr('abcdefg',b) ORDER BY +x;
} {2 4}

finish_test