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Fix an incorrect answer that might arise if a scalar query is both

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DISTINCT and contains an OFFSET clause.
[forum:/forumpost/2025-12-03T09:25:59Z|Forum post 2025-12-03T09:25:59Z].

FossilOrigin-Name: aef5397569d65d2971367b0278fe3a6f42544cf771572e7d046e2472f052364d
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drh
2025-12-04 00:05:49 +00:00
parent 27a7770f52 ab63da3f1c
commit 2121fc4141
5 changed files with 99 additions and 13 deletions
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src/expr.c
+15 -2
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@@ -3897,9 +3897,22 @@ int sqlite3CodeSubselect(Parse *pParse, Expr *pExpr){
pParse->nMem += nReg;
if( pExpr->op==TK_SELECT ){
dest.eDest = SRT_Mem;
dest.iSdst = dest.iSDParm;
if( (pSel->selFlags&SF_Distinct) && pSel->pLimit && pSel->pLimit->pRight ){
/* If there is both a DISTINCT and an OFFSET clause, then allocate
** a separate dest.iSdst array for sqlite3Select() and other
** routines to populate. In this case results will be copied over
** into the dest.iSDParm array only after OFFSET processing. This
** ensures that in the case where OFFSET excludes all rows, the
** dest.iSDParm array is not left populated with the contents of the
** last row visited - it should be all NULLs if all rows were
** excluded by OFFSET. */
dest.iSdst = pParse->nMem+1;
pParse->nMem += nReg;
}else{
dest.iSdst = dest.iSDParm;
}
dest.nSdst = nReg;
sqlite3VdbeAddOp3(v, OP_Null, 0, dest.iSDParm, dest.iSDParm+nReg-1);
sqlite3VdbeAddOp3(v, OP_Null, 0, dest.iSDParm, pParse->nMem);
VdbeComment((v, "Init subquery result"));
}else{
dest.eDest = SRT_Exists;