greenplumn CJoinOrderMinCard 代码
文件路径：/src/backend/gporca/libgpopt/src/xforms/CJoinOrderMinCard.cpp
/---------------------------------------------------------------------------
/ Greenplum Database
/ Copyright (C) 2012 EMC Corp.
/
/ @filename:
/ CJoinOrderMinCard.cpp
/
/ @doc:
/ Implementation of cardinality-based join order generation
/---------------------------------------------------------------------------
#include "gpopt/xforms/CJoinOrderMinCard.h"
#include "gpos/base.h"
#include "gpos/common/CBitSet.h"
#include "gpos/common/clibwrapper.h"
#include "gpos/io/COstreamString.h"
#include "gpos/string/CWStringDynamic.h"
#include "gpopt/base/CColRefSetIter.h"
#include "gpopt/base/CDrvdPropScalar.h"
#include "gpopt/base/CUtils.h"
#include "gpopt/operators/CNormalizer.h"
#include "gpopt/operators/CPredicateUtils.h"
using namespace gpopt;
/---------------------------------------------------------------------------
/ @function:
/ CJoinOrderMinCard::CJoinOrderMinCard
/
/ @doc:
/ Ctor
/
/---------------------------------------------------------------------------
CJoinOrderMinCard::CJoinOrderMinCard(CMemoryPool *mp,
CExpressionArray *pdrgpexprComponents,
CExpressionArray *pdrgpexprConjuncts)
: CJoinOrder(mp, pdrgpexprComponents, pdrgpexprConjuncts,
true /* m_include_loj_childs */),
m_pcompResult(nullptr)
{
#ifdef GPOS_DEBUG
for (ULONG ul = 0; ul < m_ulComps; ul++)
{
GPOS_ASSERT(nullptr != m_rgpcomp[ul]->m_pexpr->Pstats() &&
"stats were not derived on input component");
}
#endif / GPOS_DEBUG
}
/---------------------------------------------------------------------------
/ @function:
/ CJoinOrderMinCard::~CJoinOrderMinCard
/
/ @doc:
/ Dtor
/
/---------------------------------------------------------------------------
CJoinOrderMinCard::~CJoinOrderMinCard()
{
CRefCount::SafeRelease(m_pcompResult);
}
/---------------------------------------------------------------------------
/ @function:
/ CJoinOrderMinCard::PexprExpand
/
/ @doc:
/ Create join order
/
/---------------------------------------------------------------------------
CExpression *
CJoinOrderMinCard::PexprExpand()
{
GPOS_ASSERT(nullptr == m_pcompResult && "join order is already expanded");
m_pcompResult = GPOS_NEW(m_mp) SComponent(m_mp, nullptr /*pexpr*/);
ULONG ulCoveredComps = 0;
while (ulCoveredComps < m_ulComps)
{
CDouble dMinRows(0.0);
SComponent *pcompBest =
nullptr; / best component to be added to current result
SComponent *pcompBestResult =
nullptr; / result after adding best component
for (ULONG ul = 0; ul < m_ulComps; ul++)
{
SComponent *pcompCurrent = m_rgpcomp[ul];
if (pcompCurrent->m_fUsed)
{
/ used components are already included in current result
continue;
}
if (!IsValidJoinCombination(m_pcompResult, pcompCurrent))
{
continue;
}
/ combine component with current result and derive stats
CJoinOrder::SComponent *pcompTemp =
PcompCombine(m_pcompResult, pcompCurrent);
DeriveStats(pcompTemp->m_pexpr);
CDouble rows = pcompTemp->m_pexpr->Pstats()->Rows();
if (nullptr == pcompBestResult || rows < dMinRows)
{
pcompBest = pcompCurrent;
dMinRows = rows;
pcompTemp->AddRef();
CRefCount::SafeRelease(pcompBestResult);
pcompBestResult = pcompTemp;
}
pcompTemp->Release();
}
#ifndef GPOS_DEBUG
if (pcompBest == nullptr)
{
/ ideally we should never have the best result as null
GPOS_RAISE(CException::ExmaInvalid, CException::ExmiInvalid,
GPOS_WSZ_LIT("Unable to find best join component"));
}
#endif
GPOS_ASSERT(nullptr != pcompBestResult);
/ mark best component as used.
/ we will never have p_compBest as NULL, as
/ we iterate over all the components to find the possible
/ join alternative, thus there will be atleast one component
/ marked as pcompBest
pcompBest->m_fUsed = true;
m_pcompResult->Release();
m_pcompResult = pcompBestResult;
/ mark used edges to avoid including them multiple times
MarkUsedEdges(m_pcompResult);
ulCoveredComps++;
}
GPOS_ASSERT(nullptr != m_pcompResult->m_pexpr);
CExpression *pexprResult = m_pcompResult->m_pexpr;
pexprResult->AddRef();
return pexprResult;
}
/---------------------------------------------------------------------------
/ @function:
/ CJoinOrderMinCard::OsPrint
/
/ @doc:
/ Print created join order
/
/---------------------------------------------------------------------------
IOstream &
CJoinOrderMinCard::OsPrint(IOstream &os) const
{
if (nullptr != m_pcompResult->m_pexpr)
{
os << *m_pcompResult->m_pexpr;
}
return os;
}
/ EOF
相关信息
相关文章
greenplumn CJoinOrderGreedy 源码
greenplumn CSubqueryHandler 源码
greenplumn CXformCTEAnchor2Sequence 源码