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ORCA: handle INDF predicate in PdxlnMergeJoin #1756

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ORCA: handle INDF predicate in PdxlnMergeJoin #1756

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51 changes: 28 additions & 23 deletions src/backend/gporca/libgpopt/src/translate/CTranslatorExprToDXL.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4964,41 +4964,46 @@ CTranslatorExprToDXL::PdxlnMergeJoin(CExpression *pexprMJ,
// At this point, they all better be merge joinable
GPOS_ASSERT(CPhysicalJoin::FMergeJoinCompatible(
pexprPred, pexprOuterChild, pexprInnerChild));
CExpression *pexprPredOuter = (*pexprPred)[0];
CExpression *pexprPredInner = (*pexprPred)[1];

// align extracted columns with outer and inner children of the join
CColRefSet *pcrsOuterChild = pexprOuterChild->DeriveOutputColumns();
CColRefSet *pcrsPredInner = pexprPredInner->DeriveUsedColumns();
// Extract the two key columns out of pexprPred. Plain equality
// is `a = b` (binary ScalarCmp) but NULL-safe equality (INDF) is
// `NOT (a IS DISTINCT FROM b)`, a *unary* NOT around the binary
// IsDistinctFrom. Indexing [0]/[1] directly works for equality
// but accesses out of bounds for INDF.
CExpression *pexprPredOuter = nullptr;
CExpression *pexprPredInner = nullptr;
IMDId *mdid_scop = nullptr;
CPhysicalJoin::AlignJoinKeyOuterInner(pexprPred, pexprOuterChild,
pexprInnerChild, &pexprPredOuter,
&pexprPredInner, &mdid_scop);

#ifdef GPOS_DEBUG
CColRefSet *pcrsOuterChild = pexprOuterChild->DeriveOutputColumns();
CColRefSet *pcrsInnerChild = pexprInnerChild->DeriveOutputColumns();
CColRefSet *pcrsPredOuter = pexprPredOuter->DeriveUsedColumns();
CColRefSet *pcrsPredInner = pexprPredInner->DeriveUsedColumns();
GPOS_ASSERT(pcrsOuterChild->ContainsAll(pcrsPredOuter) &&
pcrsInnerChild->ContainsAll(pcrsPredInner) &&
"merge join keys are not aligned with children");
#endif

if (pcrsOuterChild->ContainsAll(pcrsPredInner))
pexprPredOuter->AddRef();
pexprPredInner->AddRef();
CExpression *pexprPredNew;
if (CPredicateUtils::IsEqualityOp(pexprPred))
{
GPOS_ASSERT(pcrsInnerChild->ContainsAll(pcrsPredOuter));
std::swap(pexprPredOuter, pexprPredInner);
#ifdef GPOS_DEBUG
std::swap(pcrsPredOuter, pcrsPredInner);
#endif

pexprPredOuter->AddRef();
pexprPredInner->AddRef();
pexprPred =
CUtils::PexprScalarEqCmp(m_mp, pexprPredOuter, pexprPredInner);
pexprPredNew = CUtils::PexprScalarCmp(m_mp, pexprPredOuter,
pexprPredInner, mdid_scop);
}
else
{
pexprPred->AddRef();
GPOS_ASSERT(CPredicateUtils::FINDF(pexprPred));
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@leborchuk leborchuk May 20, 2026

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Is it possible to have INDF for merge joins? Because in CPhysicalJoin::FMergeJoinCompatible we check:

// Only merge join between ScalarIdents of the same types is currently supported
	if (CPredicateUtils::FEqIdentsOfSameType(pexprPred))
	{
		pexprPredOuter = (*pexprPred)[0];
		pexprPredInner = (*pexprPred)[1];
		mdid_scop = CScalarCmp::PopConvert(pexprPred->Pop())->MdIdOp();
		GPOS_ASSERT(CUtils::FScalarIdent(pexprPredOuter));
		GPOS_ASSERT(CUtils::FScalarIdent(pexprPredInner));
	}
	else
	{
		return false;
	}

So the old code should work since we always check only for valid merge join operands.

Maybe we want to change it in future PR's?

pexprPredNew = CUtils::PexprINDF(m_mp, pexprPredOuter,
pexprPredInner, mdid_scop);
}

GPOS_ASSERT(pcrsOuterChild->ContainsAll(pcrsPredOuter) &&
pcrsInnerChild->ContainsAll(pcrsPredInner) &&
"merge join keys are not aligned with children");

dxlnode_merge_conds->AddChild(PdxlnScalar(pexprPred));
pexprPred->Release();
dxlnode_merge_conds->AddChild(PdxlnScalar(pexprPredNew));
pexprPredNew->Release();
}
pdrgpexprPredicates->Release();

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