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Overview
Comment:Replace the magic number (-2) with its symbol XN_EXPR in the exprMightBeIndexed() routine. No logic changes.
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SHA1: d4a5af69cc3bde6f8c02075c07b4d47a0252392d
User & Date: drh 2016-08-19 19:58:06
Context
2016-08-20
00:07
Change the way TK_SELECT_COLUMN is handled so that the subquery is only generated once even if part of the vector comparison is used for indexing and the other part is now. This change also is a pathway to vector assignment in UPDATE statements. check-in: d8feea7d user: drh tags: rowvalue
2016-08-19
19:58
Replace the magic number (-2) with its symbol XN_EXPR in the exprMightBeIndexed() routine. No logic changes. check-in: d4a5af69 user: drh tags: rowvalue
19:12
Improved comments on sqlite3CodeSubquery(). No changes to code. check-in: acea4ee1 user: drh tags: rowvalue
Changes
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Changes to src/whereexpr.c.

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/*
** Expression pExpr is one operand of a comparison operator that might
** be useful for indexing.  This routine checks to see if pExpr appears
** in any index.  Return TRUE (1) if pExpr is an indexed term and return
** FALSE (0) if not.  If TRUE is returned, also set *piCur to the cursor
** number of the table that is indexed and *piColumn to the column number
** of the column that is indexed, or -2 if an expression is being indexed.

**
** If pExpr is a TK_COLUMN column reference, then this routine always returns
** true even if that particular column is not indexed, because the column
** might be added to an automatic index later.
*/
static int exprMightBeIndexed(
  SrcList *pFrom,        /* The FROM clause */
................................................................................
  if( mPrereq==0 ) return 0;                 /* No table references */
  if( (mPrereq&(mPrereq-1))!=0 ) return 0;   /* Refs more than one table */
  for(i=0; mPrereq>1; i++, mPrereq>>=1){}
  iCur = pFrom->a[i].iCursor;
  for(pIdx=pFrom->a[i].pTab->pIndex; pIdx; pIdx=pIdx->pNext){
    if( pIdx->aColExpr==0 ) continue;
    for(i=0; i<pIdx->nKeyCol; i++){
      if( pIdx->aiColumn[i]!=(-2) ) continue;
      if( sqlite3ExprCompare(pExpr, pIdx->aColExpr->a[i].pExpr, iCur)==0 ){
        *piCur = iCur;
        *piColumn = -2;
        return 1;
      }
    }
  }
  return 0;
}








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/*
** Expression pExpr is one operand of a comparison operator that might
** be useful for indexing.  This routine checks to see if pExpr appears
** in any index.  Return TRUE (1) if pExpr is an indexed term and return
** FALSE (0) if not.  If TRUE is returned, also set *piCur to the cursor
** number of the table that is indexed and *piColumn to the column number
** of the column that is indexed, or XN_EXPR (-2) if an expression is being
** indexed.
**
** If pExpr is a TK_COLUMN column reference, then this routine always returns
** true even if that particular column is not indexed, because the column
** might be added to an automatic index later.
*/
static int exprMightBeIndexed(
  SrcList *pFrom,        /* The FROM clause */
................................................................................
  if( mPrereq==0 ) return 0;                 /* No table references */
  if( (mPrereq&(mPrereq-1))!=0 ) return 0;   /* Refs more than one table */
  for(i=0; mPrereq>1; i++, mPrereq>>=1){}
  iCur = pFrom->a[i].iCursor;
  for(pIdx=pFrom->a[i].pTab->pIndex; pIdx; pIdx=pIdx->pNext){
    if( pIdx->aColExpr==0 ) continue;
    for(i=0; i<pIdx->nKeyCol; i++){
      if( pIdx->aiColumn[i]!=XN_EXPR ) continue;
      if( sqlite3ExprCompare(pExpr, pIdx->aColExpr->a[i].pExpr, iCur)==0 ){
        *piCur = iCur;
        *piColumn = XN_EXPR;
        return 1;
      }
    }
  }
  return 0;
}