greenplumn CXformExpandNAryJoinMinCard 源码
greenplumn CXformExpandNAryJoinMinCard 代码
文件路径:/src/backend/gporca/libgpopt/src/xforms/CXformExpandNAryJoinMinCard.cpp
//---------------------------------------------------------------------------
// Greenplum Database
// Copyright (C) 2012 EMC Corp.
//
// @filename:
// CXformExpandNAryJoinMinCard.cpp
//
// @doc:
// Implementation of n-ary join expansion based on cardinality
// of intermediate results
//---------------------------------------------------------------------------
#include "gpopt/xforms/CXformExpandNAryJoinMinCard.h"
#include "gpos/base.h"
#include "gpopt/base/CUtils.h"
#include "gpopt/operators/CLogicalNAryJoin.h"
#include "gpopt/operators/CNormalizer.h"
#include "gpopt/operators/CPatternMultiTree.h"
#include "gpopt/operators/CPatternTree.h"
#include "gpopt/operators/CPredicateUtils.h"
#include "gpopt/xforms/CJoinOrderMinCard.h"
#include "gpopt/xforms/CXformUtils.h"
using namespace gpopt;
//---------------------------------------------------------------------------
// @function:
// CXformExpandNAryJoinMinCard::CXformExpandNAryJoinMinCard
//
// @doc:
// Ctor
//
//---------------------------------------------------------------------------
CXformExpandNAryJoinMinCard::CXformExpandNAryJoinMinCard(CMemoryPool *mp)
: CXformExploration(
// pattern
GPOS_NEW(mp) CExpression(
mp, GPOS_NEW(mp) CLogicalNAryJoin(mp),
GPOS_NEW(mp) CExpression(mp, GPOS_NEW(mp) CPatternMultiTree(mp)),
GPOS_NEW(mp) CExpression(mp, GPOS_NEW(mp) CPatternTree(mp))))
{
}
//---------------------------------------------------------------------------
// @function:
// CXformExpandNAryJoinMinCard::Exfp
//
// @doc:
// Compute xform promise for a given expression handle
//
//---------------------------------------------------------------------------
CXform::EXformPromise
CXformExpandNAryJoinMinCard::Exfp(CExpressionHandle &exprhdl) const
{
return CXformUtils::ExfpExpandJoinOrder(exprhdl, this);
}
//---------------------------------------------------------------------------
// @function:
// CXformExpandNAryJoinMinCard::Transform
//
// @doc:
// Actual transformation of n-ary join to cluster of inner joins
//
//---------------------------------------------------------------------------
void
CXformExpandNAryJoinMinCard::Transform(CXformContext *pxfctxt,
CXformResult *pxfres,
CExpression *pexpr) const
{
GPOS_ASSERT(nullptr != pxfctxt);
GPOS_ASSERT(nullptr != pxfres);
GPOS_ASSERT(FPromising(pxfctxt->Pmp(), this, pexpr));
GPOS_ASSERT(FCheckPattern(pexpr));
CMemoryPool *mp = pxfctxt->Pmp();
const ULONG arity = pexpr->Arity();
GPOS_ASSERT(arity >= 3);
CExpressionArray *pdrgpexpr = GPOS_NEW(mp) CExpressionArray(mp);
for (ULONG ul = 0; ul < arity - 1; ul++)
{
CExpression *pexprChild = (*pexpr)[ul];
pexprChild->AddRef();
pdrgpexpr->Append(pexprChild);
}
CExpression *pexprScalar = (*pexpr)[arity - 1];
CExpressionArray *pdrgpexprPreds =
CPredicateUtils::PdrgpexprConjuncts(mp, pexprScalar);
// create a join order based on cardinality of intermediate results
CJoinOrderMinCard jomc(mp, pdrgpexpr, pdrgpexprPreds);
CExpression *pexprResult = jomc.PexprExpand();
// normalize resulting expression
CExpression *pexprNormalized = CNormalizer::PexprNormalize(mp, pexprResult);
pexprResult->Release();
pxfres->Add(pexprNormalized);
}
// EOF
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