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Proof of concept for the ability to use the expression columns in an index

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on expressions in place of equivalent expressions in the result set or in
the WHERE clause.  This check-in compiles but is mostly untested.

FossilOrigin-Name: a52ef2ad7c0e14b78b801f16a1f6ea8d8fa9ae5d7d810e18dd24c600b662a312
This commit is contained in:
drh
2017-04-07 19:41:31 +00:00
parent 54e2efcd2f
commit aca19e19a8
9 changed files with 85 additions and 15 deletions
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59
src/wherecode.c
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@ -1039,6 +1039,61 @@ static void codeExprOrVector(Parse *pParse, Expr *p, int iReg, int nReg){
}
}
#if 1 /* INDEXEXPRTRANS */
typedef struct IdxExprTrans {
Expr *pIdxExpr; /* The index expression */
int iTabCur; /* The cursor of the corresponding table */
int iIdxCur; /* The cursor for the index */
int iIdxCol; /* The column for the index */
} IdxExprTrans;
static int whereIndexExprTransNode(Walker *p, Expr *pExpr){
IdxExprTrans *pX = p->u.pIdxTrans;
if( sqlite3ExprCompare(pExpr, pX->pIdxExpr, pX->iTabCur)==0 ){
pExpr->op = TK_COLUMN;
pExpr->iTable = pX->iIdxCur;
pExpr->iColumn = pX->iIdxCol;
pExpr->pTab = 0;
return WRC_Prune;
}else{
return WRC_Continue;
}
}
/*
** For an indexes on expression X, locate every instance of expression X in pExpr
** and change that subexpression into a reference to the appropriate column of
** the index.
*/
static void whereIndexExprTrans(
Index *pIdx, /* The Index */
int iTabCur, /* Cursor of the table that is being indexed */
int iIdxCur, /* Cursor of the index itself */
WhereInfo *pWInfo /* Transform expressions in this WHERE clause */
){
int iIdxCol; /* Column number of the index */
ExprList *aColExpr; /* Expressions that are indexed */
Walker w;
IdxExprTrans x;
aColExpr = pIdx->aColExpr;
if( aColExpr==0 ) return; /* Not an index on expressions */
memset(&w, 0, sizeof(w));
w.xExprCallback = whereIndexExprTransNode;
w.u.pIdxTrans = &x;
x.iTabCur = iTabCur;
x.iIdxCur = iIdxCur;
for(iIdxCol=0; iIdxCol<aColExpr->nExpr; iIdxCol++){
if( pIdx->aiColumn[iIdxCol]!=XN_EXPR ) continue;
assert( aColExpr->a[iIdxCol].pExpr!=0 );
x.iIdxCol = iIdxCol;
x.pIdxExpr = aColExpr->a[iIdxCol].pExpr;
sqlite3WalkExpr(&w, pWInfo->pWhere);
sqlite3WalkExprList(&w, pWInfo->pOrderBy);
sqlite3WalkExprList(&w, pWInfo->pResultSet);
}
}
#endif
/*
** Generate code for the start of the iLevel-th loop in the WHERE clause
** implementation described by pWInfo.
@ -1620,6 +1675,10 @@ Bitmask sqlite3WhereCodeOneLoopStart(
iRowidReg, pPk->nKeyCol); VdbeCoverage(v);
}
#if 1 /* INDEXEXPRTANS */
whereIndexExprTrans(pIdx, iCur, iIdxCur, pWInfo);
#endif
/* Record the instruction used to terminate the loop. */
if( pLoop->wsFlags & WHERE_ONEROW ){
pLevel->op = OP_Noop;