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When a scalar subquery has a pre-existing "LIMIT X" then change it to

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"LIMIT X<>0" rather than just "LIMIT 1" so that if X is 0 the limit
will still be zero.  Ticket [99cd4807dc03f178]

FossilOrigin-Name: 82e5dcf5c1d500ed82f398b38fdae0f30033804e897fbab3c10f1e15e2abedef
This commit is contained in:
drh
2019-09-23 11:55:22 +00:00
parent b7fc7c8556
commit 7ca1347f59
3 changed files with 19 additions and 9 deletions
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14
src/expr.c
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@@ -2959,11 +2959,21 @@ int sqlite3CodeSubselect(Parse *pParse, Expr *pExpr){
sqlite3VdbeAddOp2(v, OP_Integer, 0, dest.iSDParm);
VdbeComment((v, "Init EXISTS result"));
}
pLimit = sqlite3ExprAlloc(pParse->db, TK_INTEGER,&sqlite3IntTokens[1], 0);
if( pSel->pLimit ){
sqlite3ExprDelete(pParse->db, pSel->pLimit->pLeft);
/* The subquery already has a limit. If the pre-existing limit is X
** then make the new limit X<>0 so that the new limit is either 1 or 0 */
sqlite3 *db = pParse->db;
pLimit = sqlite3ExprAlloc(db, TK_INTEGER, &sqlite3IntTokens[0], 0);
if( pLimit ){
pLimit->affExpr = SQLITE_AFF_NUMERIC;
pLimit = sqlite3PExpr(pParse, TK_NE,
sqlite3ExprDup(db, pSel->pLimit->pLeft, 0), pLimit);
}
sqlite3ExprDelete(db, pSel->pLimit->pLeft);
pSel->pLimit->pLeft = pLimit;
}else{
/* If there is no pre-existing limit add a limit of 1 */
pLimit = sqlite3ExprAlloc(pParse->db, TK_INTEGER, &sqlite3IntTokens[1], 0);
pSel->pLimit = sqlite3PExpr(pParse, TK_LIMIT, pLimit, 0);
}
pSel->iLimit = 0;