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Tighter VDBE code for the WHERE_DISTINCT_ORDERED case of DISTINCT keyword

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handling.

FossilOrigin-Name: 94b48064db3cbb43e911fdf7183218b08146ec10
This commit is contained in:
drh
2012-09-19 21:15:46 +00:00
parent ae651d614e
commit 053a128f55
6 changed files with 73 additions and 32 deletions
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32
src/select.c
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@@ -4059,29 +4059,35 @@ int sqlite3Select(
if( pWInfo->eDistinct==WHERE_DISTINCT_ORDERED ){
int iJump;
int iExpr;
int iFlag = ++pParse->nMem;
int nExpr = pEList->nExpr;
int iBase = pParse->nMem+1;
int iBase2 = iBase + pEList->nExpr;
int iBase2 = iBase + nExpr;
pParse->nMem += (pEList->nExpr*2);
/* Change the OP_OpenEphemeral coded earlier to an OP_Integer. The
** OP_Integer initializes the "first row" flag. */
pOp->opcode = OP_Integer;
/* Change the OP_OpenEphemeral coded earlier to an OP_Null
** sets the MEM_Cleared bit on the first register of the
** previous value. This will cause the OP_Ne below to always
** fail on the first iteration of the loop even if the first
** row is all NULLs.
*/
pOp->opcode = OP_Null;
pOp->p1 = 1;
pOp->p2 = iFlag;
pOp->p2 = iBase2;
pOp->p3 = iBase2 + nExpr - 1;
sqlite3ExprCodeExprList(pParse, pEList, iBase, 1);
iJump = sqlite3VdbeCurrentAddr(v) + 1 + pEList->nExpr + 1 + 1;
sqlite3VdbeAddOp2(v, OP_If, iFlag, iJump-1);
for(iExpr=0; iExpr<pEList->nExpr; iExpr++){
iJump = sqlite3VdbeCurrentAddr(v) + pEList->nExpr;
for(iExpr=0; iExpr<nExpr; iExpr++){
CollSeq *pColl = sqlite3ExprCollSeq(pParse, pEList->a[iExpr].pExpr);
sqlite3VdbeAddOp3(v, OP_Ne, iBase+iExpr, iJump, iBase2+iExpr);
if( iExpr<nExpr-1 ){
sqlite3VdbeAddOp3(v, OP_Ne, iBase+iExpr, iJump, iBase2+iExpr);
}else{
sqlite3VdbeAddOp3(v, OP_Eq, iBase+iExpr, pWInfo->iContinue,
iBase2+iExpr);
}
sqlite3VdbeChangeP4(v, -1, (const char *)pColl, P4_COLLSEQ);
sqlite3VdbeChangeP5(v, SQLITE_NULLEQ);
}
sqlite3VdbeAddOp2(v, OP_Goto, 0, pWInfo->iContinue);
sqlite3VdbeAddOp2(v, OP_Integer, 0, iFlag);
assert( sqlite3VdbeCurrentAddr(v)==iJump );
sqlite3VdbeAddOp3(v, OP_Move, iBase, iBase2, pEList->nExpr);
}else{