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When flattening the right operand of a LEFT JOIN

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(check-in [41c27bc0ff1d3135]), ensure that the OP_IfNullRow opcode does not
NULL-out a subquery result that was computed within OP_Once.  This fixes
the problem problem reported by
[forum:/forumpost/402f05296d|forum post 402f05296d].

FossilOrigin-Name: 8fe13f7a5e5eb798189acb25a608df7a94c2f5cc83463331a048b779c7890c82
This commit is contained in:
drh
2023-03-02 13:49:50 +00:00
parent c355f6c839
commit 3f23ce664e
4 changed files with 40 additions and 16 deletions
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20
src/expr.c
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@@ -4833,16 +4833,22 @@ expr_code_doover:
break;
}
}
addrINR = sqlite3VdbeAddOp1(v, OP_IfNullRow, pExpr->iTable);
/* Temporarily disable factoring of constant expressions, since
** even though expressions may appear to be constant, they are not
** really constant because they originate from the right-hand side
** of a LEFT JOIN. */
pParse->okConstFactor = 0;
addrINR = sqlite3VdbeAddOp3(v, OP_IfNullRow, pExpr->iTable, 0, target);
/* The OP_IfNullRow opcode above can overwrite the result register with
** NULL. So we have to ensure that the result register is not a value
** that is suppose to be a constant. Two defenses are needed:
** (1) Temporarily disable factoring of constant expressions
** (2) Make sure the computed value really is stored in register
** "target" and not someplace else.
*/
pParse->okConstFactor = 0; /* note (1) above */
inReg = sqlite3ExprCodeTarget(pParse, pExpr->pLeft, target);
pParse->okConstFactor = okConstFactor;
if( inReg!=target ){ /* note (2) above */
sqlite3VdbeAddOp2(v, OP_SCopy, inReg, target);
inReg = target;
}
sqlite3VdbeJumpHere(v, addrINR);
sqlite3VdbeChangeP3(v, addrINR, inReg);
break;
}