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Improved comments. Fix a problem when an indexed expression is used in an

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ORDER BY clause.

FossilOrigin-Name: c59eaf2b7cd2596733f349fc0fe979f71fd29bd73152a0c57066e0b69d5b7a4a
This commit is contained in:
drh
2017-04-11 01:01:27 +00:00
parent 2f8b37850c
commit eac5fc0476
4 changed files with 42 additions and 20 deletions
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19
src/wherecode.c
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@ -1039,7 +1039,10 @@ static void codeExprOrVector(Parse *pParse, Expr *p, int iReg, int nReg){
}
}
#if 1 /* INDEXEXPRTRANS */
/* An instance of the IdxExprTrans object carries information about a
** mapping from an expression on table columns into a column in an index
** down through the Walker.
*/
typedef struct IdxExprTrans {
Expr *pIdxExpr; /* The index expression */
int iTabCur; /* The cursor of the corresponding table */
@ -1047,6 +1050,12 @@ typedef struct IdxExprTrans {
int iIdxCol; /* The column for the index */
} IdxExprTrans;
/* The walker node callback used to transform matching expressions into
** a reference to an index column for an index on an expression.
**
** If pExpr matches, then transform it into a reference to the index column
** that contains the value of pExpr.
*/
static int whereIndexExprTransNode(Walker *p, Expr *pExpr){
IdxExprTrans *pX = p->u.pIdxTrans;
if( sqlite3ExprCompare(pExpr, pX->pIdxExpr, pX->iTabCur)==0 ){
@ -1092,7 +1101,6 @@ static void whereIndexExprTrans(
sqlite3WalkExprList(&w, pWInfo->pResultSet);
}
}
#endif
/*
** Generate code for the start of the iLevel-th loop in the WHERE clause
@ -1675,9 +1683,12 @@ Bitmask sqlite3WhereCodeOneLoopStart(
iRowidReg, pPk->nKeyCol); VdbeCoverage(v);
}
#if 1 /* INDEXEXPRTANS */
/* If pIdx is an index on one or more expressions, then look through
** all the expressions in pWInfo and try to transform matching expressions
** into reference to index columns.
*/
whereIndexExprTrans(pIdx, iCur, iIdxCur, pWInfo);
#endif
/* Record the instruction used to terminate the loop. */
if( pLoop->wsFlags & WHERE_ONEROW ){