greenplumn CXformExpandNAryJoinDP 代码
文件路径：/src/backend/gporca/libgpopt/src/xforms/CXformExpandNAryJoinDP.cpp
/---------------------------------------------------------------------------
/ Greenplum Database
/ Copyright (C) 2013 EMC Corp.
/
/ @filename:
/ CXformExpandNAryJoinDP.cpp
/
/ @doc:
/ Implementation of n-ary join expansion using dynamic programming
/---------------------------------------------------------------------------
#include "gpopt/xforms/CXformExpandNAryJoinDP.h"
#include "gpos/base.h"
#include "gpopt/base/COptCtxt.h"
#include "gpopt/base/CUtils.h"
#include "gpopt/engine/CHint.h"
#include "gpopt/operators/CLogicalNAryJoin.h"
#include "gpopt/operators/CNormalizer.h"
#include "gpopt/operators/CPatternMultiLeaf.h"
#include "gpopt/operators/CPatternMultiTree.h"
#include "gpopt/operators/CPredicateUtils.h"
#include "gpopt/optimizer/COptimizerConfig.h"
#include "gpopt/xforms/CJoinOrderDP.h"
#include "gpopt/xforms/CXformUtils.h"
using namespace gpopt;
/---------------------------------------------------------------------------
/ @function:
/ CXformExpandNAryJoinDP::CXformExpandNAryJoinDP
/
/ @doc:
/ Ctor
/
/---------------------------------------------------------------------------
CXformExpandNAryJoinDP::CXformExpandNAryJoinDP(CMemoryPool *mp)
: CXformExploration(
/ pattern
GPOS_NEW(mp) CExpression(
mp, GPOS_NEW(mp) CLogicalNAryJoin(mp),
GPOS_NEW(mp) CExpression(mp, GPOS_NEW(mp) CPatternMultiLeaf(mp)),
GPOS_NEW(mp) CExpression(mp, GPOS_NEW(mp) CPatternTree(mp))))
{
}
/---------------------------------------------------------------------------
/ @function:
/ CXformExpandNAryJoinDP::Exfp
/
/ @doc:
/ Compute xform promise for a given expression handle
/
/---------------------------------------------------------------------------
CXform::EXformPromise
CXformExpandNAryJoinDP::Exfp(CExpressionHandle &exprhdl) const
{
COptimizerConfig *optimizer_config =
COptCtxt::PoctxtFromTLS()->GetOptimizerConfig();
const CHint *phint = optimizer_config->GetHint();
const ULONG arity = exprhdl.Arity();
/ since the last child of the join operator is a scalar child
/ defining the join predicate, ignore it.
const ULONG ulRelChild = arity - 1;
if (ulRelChild > phint->UlJoinOrderDPLimit())
{
return CXform::ExfpNone;
}
return CXformUtils::ExfpExpandJoinOrder(exprhdl, this);
}
/---------------------------------------------------------------------------
/ @function:
/ CXformExpandNAryJoinDP::Transform
/
/ @doc:
/ Actual transformation of n-ary join to cluster of inner joins using
/ dynamic programming
/
/---------------------------------------------------------------------------
void
CXformExpandNAryJoinDP::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 join order using dynamic programming
CJoinOrderDP jodp(mp, pdrgpexpr, pdrgpexprPreds);
CExpression *pexprResult = jodp.PexprExpand();
if (nullptr != pexprResult)
{
/ normalize resulting expression
CExpression *pexprNormalized =
CNormalizer::PexprNormalize(mp, pexprResult);
pexprResult->Release();
pxfres->Add(pexprNormalized);
const ULONG UlTopKJoinOrders = jodp.PdrgpexprTopK()->Size();
for (ULONG ul = 0; ul < UlTopKJoinOrders; ul++)
{
CExpression *pexprJoinOrder = (*jodp.PdrgpexprTopK())[ul];
if (pexprJoinOrder != pexprResult)
{
/ We should consider normalizing this expression before inserting it, as we do for pexprResult
pexprJoinOrder->AddRef();
pxfres->Add(pexprJoinOrder);
}
}
}
}
/ EOF
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