greenplumn CXformJoinSwap 源码
greenplumn CXformJoinSwap 代码
文件路径：/src/backend/gporca/libgpopt/include/gpopt/xforms/CXformJoinSwap.h
//---------------------------------------------------------------------------
// Greenplum Database
// Copyright (C) 2012 EMC Corp.
//
// @filename:
// CXformJoinSwap.h
//
// @doc:
// Join swap transformation
//---------------------------------------------------------------------------
#ifndef GPOPT_CXformJoinSwap_H
#define GPOPT_CXformJoinSwap_H
#include "gpos/base.h"
#include "gpopt/operators/CPatternLeaf.h"
#include "gpopt/xforms/CXformExploration.h"
#include "gpopt/xforms/CXformUtils.h"
namespace gpopt
{
using namespace gpos;
//---------------------------------------------------------------------------
// @class:
// CXformJoinSwap
//
// @doc:
// Join swap transformation
//
//---------------------------------------------------------------------------
template <class TJoinTop, class TJoinBottom>
class CXformJoinSwap : public CXformExploration
{
private:
public:
CXformJoinSwap(const CXformJoinSwap &) = delete;
// ctor
explicit CXformJoinSwap(CMemoryPool *mp)
: CXformExploration(
// pattern
GPOS_NEW(mp) CExpression(
mp, GPOS_NEW(mp) TJoinTop(mp),
GPOS_NEW(mp) CExpression // left child is a join tree
(mp, GPOS_NEW(mp) TJoinBottom(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) CPatternLeaf(mp)) // predicate
),
GPOS_NEW(mp) CExpression // right child is a pattern leaf
(mp, GPOS_NEW(mp) CPatternLeaf(mp)),
GPOS_NEW(mp) CExpression(
mp, GPOS_NEW(mp) CPatternLeaf(mp)) // top-join predicate
))
{
}
// dtor
~CXformJoinSwap() override = default;
// compute xform promise for a given expression handle
EXformPromise
Exfp(CExpressionHandle & // exprhdl
) const override
{
return CXform::ExfpHigh;
}
// actual transform
void
Transform(CXformContext *pxfctxt, CXformResult *pxfres,
CExpression *pexpr) const override
{
GPOS_ASSERT(nullptr != pxfctxt);
GPOS_ASSERT(FPromising(pxfctxt->Pmp(), this, pexpr));
GPOS_ASSERT(FCheckPattern(pexpr));
CMemoryPool *mp = pxfctxt->Pmp();
CExpression *pexprResult =
CXformUtils::PexprSwapJoins(mp, pexpr, (*pexpr)[0]);
if (nullptr == pexprResult)
{
return;
}
pxfres->Add(pexprResult);
}
}; // class CXformJoinSwap
} // namespace gpopt
#endif // !GPOPT_CXformJoinSwap_H
// EOF
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