//---------------------------------------------------------------------------
// @function:
// CXformSelect2PartialDynamicIndexGet::Transform
//
// @doc:
// Actual transformation
//
//---------------------------------------------------------------------------
void
CXformSelect2PartialDynamicIndexGet::Transform
(
CXformContext *pxfctxt,
CXformResult *pxfres,
CExpression *pexpr
)
const
{
GPOS_ASSERT(NULL != pxfctxt);
GPOS_ASSERT(FPromising(pxfctxt->Pmp(), this, pexpr));
GPOS_ASSERT(FCheckPattern(pexpr));
IMemoryPool *pmp = pxfctxt->Pmp();
// extract components
CExpression *pexprRelational = (*pexpr)[0];
CExpression *pexprScalar = (*pexpr)[1];
// get the indexes on this relation
CLogicalDynamicGet *popGet = CLogicalDynamicGet::PopConvert(pexprRelational->Pop());
if (popGet->FPartial())
{
// already a partial dynamic get; do not try to split further
return;
}
CTableDescriptor *ptabdesc = popGet->Ptabdesc();
CMDAccessor *pmda = COptCtxt::PoctxtFromTLS()->Pmda();
const IMDRelation *pmdrel = pmda->Pmdrel(ptabdesc->Pmdid());
const ULONG ulIndices = pmdrel->UlIndices();
if (0 == ulIndices)
{
// no indexes on the table
return;
}
// array of expressions in the scalar expression
DrgPexpr *pdrgpexpr = CPredicateUtils::PdrgpexprConjuncts(pmp, pexprScalar);
GPOS_ASSERT(0 < pdrgpexpr->UlLength());
// derive the scalar and relational properties to build set of required columns
CColRefSet *pcrsOutput = CDrvdPropRelational::Pdprel(pexpr->PdpDerive())->PcrsOutput();
CColRefSet *pcrsScalarExpr = CDrvdPropScalar::Pdpscalar(pexprScalar->PdpDerive())->PcrsUsed();
CColRefSet *pcrsReqd = GPOS_NEW(pmp) CColRefSet(pmp);
pcrsReqd->Include(pcrsOutput);
pcrsReqd->Include(pcrsScalarExpr);
CPartConstraint *ppartcnstr = popGet->Ppartcnstr();
ppartcnstr->AddRef();
// find a candidate set of partial index combinations
DrgPdrgPpartdig *pdrgpdrgppartdig = CXformUtils::PdrgpdrgppartdigCandidates
(
pmp,
pmda,
pdrgpexpr,
popGet->PdrgpdrgpcrPart(),
pmdrel,
ppartcnstr,
popGet->PdrgpcrOutput(),
pcrsReqd,
pcrsScalarExpr,
NULL // pcrsAcceptedOuterRefs
);
// construct alternative partial index scan plans
const ULONG ulCandidates = pdrgpdrgppartdig->UlLength();
for (ULONG ul = 0; ul < ulCandidates; ul++)
{
DrgPpartdig *pdrgppartdig = (*pdrgpdrgppartdig)[ul];
CreatePartialIndexGetPlan(pmp, pexpr, pdrgppartdig, pmdrel, pxfres);
}
ppartcnstr->Release();
pcrsReqd->Release();
pdrgpexpr->Release();
pdrgpdrgppartdig->Release();
}
