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Fix a problem with the query optimizer for LIMIT/OFFSET queries when

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underlying query is a UNION ALL and both arms of the UNION ALL are
subqueries with an ORDER BY clause.  This bug was reported at
[forum:/forumpost/6b5e9188f0657616|forum post 6b5e9188f0657616].  The
problem was introduced in 2015 (SQLite version 3.9.0) by check-in
[4b631364354068af].  See also ticket [b65cb2c8d91f6685].

FossilOrigin-Name: 6c806f64bbc9e98891bad0868575ee2ec5d0951ceb0c71d3ed417b45d5f27561
This commit is contained in:
drh
2022-08-04 17:15:00 +00:00
parent e24a6f58ae
commit bffd5c1ece
4 changed files with 54 additions and 10 deletions
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5
src/select.c
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@@ -1688,7 +1688,7 @@ static void generateSortTail(
if( addrOnce ) sqlite3VdbeJumpHere(v, addrOnce);
addr = 1 + sqlite3VdbeAddOp2(v, OP_SorterSort, iTab, addrBreak);
VdbeCoverage(v);
codeOffset(v, p->iOffset, addrContinue);
assert( p->iLimit==0 && p->iOffset==0 );
sqlite3VdbeAddOp3(v, OP_SorterData, iTab, regSortOut, iSortTab);
bSeq = 0;
}else{
@@ -1696,6 +1696,9 @@ static void generateSortTail(
codeOffset(v, p->iOffset, addrContinue);
iSortTab = iTab;
bSeq = 1;
if( p->iOffset>0 ){
sqlite3VdbeAddOp2(v, OP_AddImm, p->iLimit, -1);
}
}
for(i=0, iCol=nKey+bSeq-1; i<nColumn; i++){
#ifdef SQLITE_ENABLE_SORTER_REFERENCES