greenplumn CXformLeftJoin2RightJoin 源码
greenplumn CXformLeftJoin2RightJoin 代码
文件路径：/src/backend/gporca/libgpopt/src/xforms/CXformLeftJoin2RightJoin.cpp
//---------------------------------------------------------------------------
// Greenplum Database
// Copyright (c) 2020 VMware, Inc.
//
// @filename:
// CXformLeftJoin2RightJoin.cpp
//
// @doc:
// Implementation of transform
//---------------------------------------------------------------------------
#include "gpopt/xforms/CXformLeftJoin2RightJoin.h"
#include "gpos/base.h"
#include "gpos/memory/CAutoMemoryPool.h"
#include "gpopt/operators/CLogicalLeftOuterJoin.h"
#include "gpopt/operators/CLogicalRightOuterJoin.h"
#include "gpopt/operators/CPatternLeaf.h"
#include "gpopt/operators/CPredicateUtils.h"
#include "gpopt/operators/CScalarProjectList.h"
using namespace gpopt;
//---------------------------------------------------------------------------
// @function:
// CXformLeftJoin2RightJoin::CXformLeftJoin2RightJoin
//
// @doc:
// ctor
//
//---------------------------------------------------------------------------
CXformLeftJoin2RightJoin::CXformLeftJoin2RightJoin(CMemoryPool *mp)
: // pattern
CXformExploration(
// pattern
GPOS_NEW(mp) CExpression(
mp, GPOS_NEW(mp) CLogicalLeftOuterJoin(mp),
GPOS_NEW(mp)
CExpression(mp, GPOS_NEW(mp) CPatternLeaf(mp)), // left child
GPOS_NEW(mp) CExpression(
mp, GPOS_NEW(mp) CPatternLeaf(mp)), // right child
GPOS_NEW(mp) CExpression(
mp, GPOS_NEW(mp) CPatternTree(mp)) // predicate tree
))
{
}
//---------------------------------------------------------------------------
// @function:
// CXformLeftJoin2RightJoin::Exfp
//
// @doc:
// Compute xform promise for a given expression handle;
//
//---------------------------------------------------------------------------
CXform::EXformPromise
CXformLeftJoin2RightJoin::Exfp(CExpressionHandle &exprhdl) const
{
// if scalar predicate has a subquery, we must have an
// equivalent logical Apply expression created during exploration;
// no need for generating a physical join
if (exprhdl.DeriveHasSubquery(2))
{
return CXform::ExfpNone;
}
return CXform::ExfpHigh;
}
//---------------------------------------------------------------------------
// @function:
// CXformLeftJoin2RightJoin::Transform
//
// @doc:
// actual transformation
//
//---------------------------------------------------------------------------
void
CXformLeftJoin2RightJoin::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();
// A ROJ is identical to a LOJ except the children are swapped
CExpression *pexprOuter = (*pexpr)[0];
CExpression *pexprInner = (*pexpr)[1];
CExpression *pexprScalar = (*pexpr)[2];
pexprOuter->AddRef();
pexprInner->AddRef();
pexprScalar->AddRef();
CExpression *pexprRightJoin =
CUtils::PexprLogicalJoin<CLogicalRightOuterJoin>(
mp, pexprInner, pexprOuter, pexprScalar);
pxfres->Add(pexprRightJoin);
}
// EOF
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