greenplumn CXformSelect2Filter 代码
文件路径：/src/backend/gporca/libgpopt/src/xforms/CXformSelect2Filter.cpp
/---------------------------------------------------------------------------
/ Greenplum Database
/ Copyright (C) 2011 EMC Corp.
/
/ @filename:
/ CXformSelect2Filter.cpp
/
/ @doc:
/ Implementation of transform
/---------------------------------------------------------------------------
#include "gpopt/xforms/CXformSelect2Filter.h"
#include "gpos/base.h"
#include "gpopt/operators/CLogicalSelect.h"
#include "gpopt/operators/CPatternLeaf.h"
#include "gpopt/operators/CPhysicalFilter.h"
using namespace gpopt;
/---------------------------------------------------------------------------
/ @function:
/ CXformSelect2Filter::CXformSelect2Filter
/
/ @doc:
/ Ctor
/
/---------------------------------------------------------------------------
CXformSelect2Filter::CXformSelect2Filter(CMemoryPool *mp)
: / pattern
CXformImplementation(GPOS_NEW(mp) CExpression(
mp, GPOS_NEW(mp) CLogicalSelect(mp),
GPOS_NEW(mp) CExpression(
mp, GPOS_NEW(mp) CPatternLeaf(mp)), / relational child
GPOS_NEW(mp)
CExpression(mp, GPOS_NEW(mp) CPatternLeaf(mp)) / predicate
))
{
}
/---------------------------------------------------------------------------
/ @function:
/ CXformSelect2Filter::Exfp
/
/ @doc:
/ Compute xform promise level for a given expression handle;
/ if scalar predicate has a subquery, then we must have an
/ equivalent logical Apply expression created during exploration;
/ no need for generating a Filter expression here
/
/---------------------------------------------------------------------------
CXform::EXformPromise
CXformSelect2Filter::Exfp(CExpressionHandle &exprhdl) const
{
if (exprhdl.DeriveHasSubquery(1))
{
return CXform::ExfpNone;
}
return CXform::ExfpHigh;
}
/---------------------------------------------------------------------------
/ @function:
/ CXformSelect2Filter::Transform
/
/ @doc:
/ Actual transformation
/
/---------------------------------------------------------------------------
void
CXformSelect2Filter::Transform(CXformContext *pxfctxt, CXformResult *pxfres,
CExpression *pexpr) const
{
GPOS_ASSERT(nullptr != pxfctxt);
GPOS_ASSERT(FPromising(pxfctxt->Pmp(), this, pexpr));
GPOS_ASSERT(FCheckPattern(pexpr));
CMemoryPool *mp = pxfctxt->Pmp();
/ extract components
CExpression *pexprRelational = (*pexpr)[0];
CExpression *pexprScalar = (*pexpr)[1];
/ addref all children
pexprRelational->AddRef();
pexprScalar->AddRef();
/ assemble physical operator
CExpression *pexprFilter = GPOS_NEW(mp) CExpression(
mp, GPOS_NEW(mp) CPhysicalFilter(mp), pexprRelational, pexprScalar);
/ add alternative to results
pxfres->Add(pexprFilter);
}
/ EOF
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