//---------------------------------------------------------------------------
// @function:
// CLogical::PcrsDeriveOuter
//
// @doc:
// Derive outer references
//
//---------------------------------------------------------------------------
CColRefSet *
CLogical::PcrsDeriveOuter
(
IMemoryPool *pmp,
CExpressionHandle &exprhdl,
CColRefSet *pcrsUsedAdditional
)
{
ULONG ulArity = exprhdl.UlArity();
CColRefSet *pcrsOuter = GPOS_NEW(pmp) CColRefSet(pmp);
// collect output columns from relational children
// and used columns from scalar children
CColRefSet *pcrsOutput = GPOS_NEW(pmp) CColRefSet(pmp);
CColRefSet *pcrsUsed = GPOS_NEW(pmp) CColRefSet(pmp);
for (ULONG i = 0; i < ulArity; i++)
{
if (exprhdl.FScalarChild(i))
{
CDrvdPropScalar *pdpscalar = exprhdl.Pdpscalar(i);
pcrsUsed->Union(pdpscalar->PcrsUsed());
}
else
{
CDrvdPropRelational *pdprel = exprhdl.Pdprel(i);
pcrsOutput->Union(pdprel->PcrsOutput());
// add outer references from relational children
pcrsOuter->Union(pdprel->PcrsOuter());
}
}
if (NULL != pcrsUsedAdditional)
{
pcrsUsed->Include(pcrsUsedAdditional);
}
// outer references are columns used by scalar child
// but are not included in the output columns of relational children
pcrsOuter->Union(pcrsUsed);
pcrsOuter->Exclude(pcrsOutput);
pcrsOutput->Release();
pcrsUsed->Release();
return pcrsOuter;
}
//---------------------------------------------------------------------------
// @function:
// CDecorrelator::FProcess
//
// @doc:
// Main driver for decorrelation of expression
//
//---------------------------------------------------------------------------
BOOL
CDecorrelator::FProcess
(
IMemoryPool *pmp,
CExpression *pexpr,
BOOL fEqualityOnly,
CExpression **ppexprDecorrelated,
DrgPexpr *pdrgpexprCorrelations
)
{
GPOS_CHECK_STACK_SIZE;
// only correlated Apply can be encountered here
GPOS_ASSERT_IMP(CUtils::FApply(pexpr->Pop()), CUtils::FCorrelatedApply(pexpr->Pop()) &&
"Apply expression is encountered by decorrelator");
CDrvdPropRelational *pdprel = CDrvdPropRelational::Pdprel(pexpr->PdpDerive());
// no outer references?
if (0 == pdprel->PcrsOuter()->CElements())
{
pexpr->AddRef();
*ppexprDecorrelated = pexpr;
return true;
}
BOOL fSuccess = FProcessOperator(pmp, pexpr, fEqualityOnly, ppexprDecorrelated, pdrgpexprCorrelations);
// in case of success make sure there are no outer references left
GPOS_ASSERT_IMP
(
fSuccess,
0 == CDrvdPropRelational::Pdprel((*ppexprDecorrelated)->PdpDerive())->PcrsOuter()->CElements()
);
return fSuccess;
}
