greenplumn CXformCollapseGbAgg 代码
文件路径：/src/backend/gporca/libgpopt/src/xforms/CXformCollapseGbAgg.cpp
/---------------------------------------------------------------------------
/ Greenplum Database
/ Copyright (C) 2013 EMC Corp.
/
/ @filename:
/ CXformCollapseGbAgg.cpp
/
/ @doc:
/ Implementation of collapsing two cascaded group-by operators
/ into a single group-by
/---------------------------------------------------------------------------
#include "gpopt/xforms/CXformCollapseGbAgg.h"
#include "gpos/base.h"
#include "gpopt/base/CUtils.h"
#include "gpopt/operators/CLogicalGbAgg.h"
#include "gpopt/operators/COperator.h"
#include "gpopt/operators/CPatternLeaf.h"
#include "gpopt/operators/CPredicateUtils.h"
using namespace gpmd;
using namespace gpopt;
/---------------------------------------------------------------------------
/ @function:
/ CXformCollapseGbAgg::CXformCollapseGbAgg
/
/ @doc:
/ Ctor
/
/---------------------------------------------------------------------------
CXformCollapseGbAgg::CXformCollapseGbAgg(CMemoryPool *mp)
: CXformExploration(
/ pattern
GPOS_NEW(mp) CExpression(
mp, GPOS_NEW(mp) CLogicalGbAgg(mp),
GPOS_NEW(mp) CExpression(
mp, GPOS_NEW(mp) CLogicalGbAgg(mp),
GPOS_NEW(mp) CExpression(
mp, GPOS_NEW(mp) CPatternLeaf(mp)), / relational child
GPOS_NEW(mp) CExpression(
mp, GPOS_NEW(mp) CPatternTree(mp)) / scalar project list
),
GPOS_NEW(mp) CExpression(
mp, GPOS_NEW(mp) CPatternTree(mp)) / scalar project list
))
{
}
/---------------------------------------------------------------------------
/ @function:
/ CXformCollapseGbAgg::Exfp
/
/ @doc:
/ Compute xform promise for a given expression handle;
/ GbAgg must be global and have non empty grouping columns
/
/---------------------------------------------------------------------------
CXform::EXformPromise
CXformCollapseGbAgg::Exfp(CExpressionHandle &exprhdl) const
{
CLogicalGbAgg *popAgg = CLogicalGbAgg::PopConvert(exprhdl.Pop());
if (!popAgg->FGlobal() || 0 == popAgg->Pdrgpcr()->Size())
{
return CXform::ExfpNone;
}
return CXform::ExfpHigh;
}
/---------------------------------------------------------------------------
/ @function:
/ CXformCollapseGbAgg::Transform
/
/ @doc:
/ Actual transformation to collapse two cascaded group by operators;
/ if the top Gb grouping columns are subset of bottom Gb grouping
/ columns AND both Gb operators do not define agg functions, we can
/ remove the bottom group by operator
/
/
/---------------------------------------------------------------------------
void
CXformCollapseGbAgg::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();
/ extract components
CLogicalGbAgg *popTopGbAgg = CLogicalGbAgg::PopConvert(pexpr->Pop());
GPOS_ASSERT(0 < popTopGbAgg->Pdrgpcr()->Size());
GPOS_ASSERT(popTopGbAgg->FGlobal());
CExpression *pexprRelational = (*pexpr)[0];
CExpression *pexprTopProjectList = (*pexpr)[1];
CLogicalGbAgg *popBottomGbAgg =
CLogicalGbAgg::PopConvert(pexprRelational->Pop());
CExpression *pexprChild = (*pexprRelational)[0];
CExpression *pexprBottomProjectList = (*pexprRelational)[1];
if (!popBottomGbAgg->FGlobal())
{
/ bottom GbAgg must be global to prevent xform from getting applied to splitted GbAggs
return;
}
if (0 < pexprTopProjectList->Arity() || 0 < pexprBottomProjectList->Arity())
{
/ exit if any of the Gb operators has an aggregate function
return;
}
#ifdef GPOS_DEBUG
/ for two cascaded GbAgg ops with no agg functions, top grouping
/ columns must be a subset of bottom grouping columns
CColRefSet *pcrsTopGrpCols =
GPOS_NEW(mp) CColRefSet(mp, popTopGbAgg->Pdrgpcr());
CColRefSet *pcrsBottomGrpCols =
GPOS_NEW(mp) CColRefSet(mp, popBottomGbAgg->Pdrgpcr());
GPOS_ASSERT(pcrsBottomGrpCols->ContainsAll(pcrsTopGrpCols));
pcrsTopGrpCols->Release();
pcrsBottomGrpCols->Release();
#endif / GPOS_DEBUG
pexprChild->AddRef();
CExpression *pexprSelect = CUtils::PexprLogicalSelect(
mp, pexprChild,
CPredicateUtils::PexprConjunction(mp, nullptr /*pdrgpexpr*/));
popTopGbAgg->AddRef();
pexprTopProjectList->AddRef();
CExpression *pexprGbAggNew = GPOS_NEW(mp)
CExpression(mp, popTopGbAgg, pexprSelect, pexprTopProjectList);
pxfres->Add(pexprGbAggNew);
}
/ EOF
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