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In the parse tree, combine LIMIT and OFFSET into a single expression rooted

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on a TK_LIMIT node, for a small code size reduction and performance increase,
and a reduction in code complexity.

FossilOrigin-Name: 3925facd942c9df663f9b29b1e6f94f6be14af8c2b99eb691bfc836b4c220826
This commit is contained in:
drh
2017-11-14 23:48:23 +00:00
parent 65efeaca83
commit 8c0833fb21
15 changed files with 92 additions and 140 deletions
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14
src/expr.c
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@@ -663,7 +663,6 @@ static void heightOfSelect(Select *p, int *pnHeight){
heightOfExpr(p->pWhere, pnHeight);
heightOfExpr(p->pHaving, pnHeight);
heightOfExpr(p->pLimit, pnHeight);
heightOfExpr(p->pOffset, pnHeight);
heightOfExprList(p->pEList, pnHeight);
heightOfExprList(p->pGroupBy, pnHeight);
heightOfExprList(p->pOrderBy, pnHeight);
@@ -1462,7 +1461,6 @@ Select *sqlite3SelectDup(sqlite3 *db, Select *pDup, int flags){
pNew->pNext = pNext;
pNew->pPrior = 0;
pNew->pLimit = sqlite3ExprDup(db, p->pLimit, flags);
pNew->pOffset = sqlite3ExprDup(db, p->pOffset, flags);
pNew->iLimit = 0;
pNew->iOffset = 0;
pNew->selFlags = p->selFlags & ~SF_UsesEphemeral;
@@ -2099,7 +2097,6 @@ static Select *isCandidateForInOpt(Expr *pX){
}
assert( p->pGroupBy==0 ); /* Has no GROUP BY clause */
if( p->pLimit ) return 0; /* Has no LIMIT clause */
assert( p->pOffset==0 ); /* No LIMIT means no OFFSET */
if( p->pWhere ) return 0; /* Has no WHERE clause */
pSrc = p->pSrc;
assert( pSrc!=0 );
@@ -2739,6 +2736,7 @@ int sqlite3CodeSubselect(
Select *pSel; /* SELECT statement to encode */
SelectDest dest; /* How to deal with SELECT result */
int nReg; /* Registers to allocate */
Expr *pLimit; /* New limit expression */
testcase( pExpr->op==TK_EXISTS );
testcase( pExpr->op==TK_SELECT );
@@ -2760,9 +2758,13 @@ int sqlite3CodeSubselect(
sqlite3VdbeAddOp2(v, OP_Integer, 0, dest.iSDParm);
VdbeComment((v, "Init EXISTS result"));
}
sqlite3ExprDelete(pParse->db, pSel->pLimit);
pSel->pLimit = sqlite3ExprAlloc(pParse->db, TK_INTEGER,
&sqlite3IntTokens[1], 0);
pLimit = sqlite3ExprAlloc(pParse->db, TK_INTEGER,&sqlite3IntTokens[1], 0);
if( pSel->pLimit ){
sqlite3ExprDelete(pParse->db, pSel->pLimit->pLeft);
pSel->pLimit->pLeft = pLimit;
}else{
pSel->pLimit = sqlite3PExpr(pParse, TK_LIMIT, pLimit, 0);
}
pSel->iLimit = 0;
pSel->selFlags &= ~SF_MultiValue;
if( sqlite3Select(pParse, pSel, &dest) ){