greenplumn CXformImplementLimit 源码
greenplumn CXformImplementLimit 代码
文件路径：/src/backend/gporca/libgpopt/src/xforms/CXformImplementLimit.cpp
//---------------------------------------------------------------------------
// Greenplum Database
// Copyright (C) 2011 EMC Corp.
//
// @filename:
// CXformImplementLimit.cpp
//
// @doc:
// Implementation of limit operator
//---------------------------------------------------------------------------
#include "gpopt/xforms/CXformImplementLimit.h"
#include "gpos/base.h"
#include "gpopt/operators/CExpressionHandle.h"
#include "gpopt/operators/CLogicalLimit.h"
#include "gpopt/operators/CPatternLeaf.h"
#include "gpopt/operators/CPhysicalLimit.h"
using namespace gpopt;
//---------------------------------------------------------------------------
// @function:
// CXformImplementLimit::CXformImplementLimit
//
// @doc:
// Ctor
//
//---------------------------------------------------------------------------
CXformImplementLimit::CXformImplementLimit(CMemoryPool *mp)
: // pattern
CXformImplementation(GPOS_NEW(mp) CExpression(
mp, GPOS_NEW(mp) CLogicalLimit(mp),
GPOS_NEW(mp) CExpression(
mp, GPOS_NEW(mp) CPatternLeaf(mp)), // relational child
GPOS_NEW(mp) CExpression(
mp, GPOS_NEW(mp) CPatternLeaf(mp)), // scalar child for offset
GPOS_NEW(mp) CExpression(
mp,
GPOS_NEW(mp) CPatternLeaf(mp)) // scalar child for number of rows
))
{
}
CXform::EXformPromise
CXformImplementLimit::Exfp(CExpressionHandle &exprhdl) const
{
// Although it is valid SQL for the limit/offset to be a subquery, Orca does
// not support it
if (exprhdl.DeriveHasSubquery(1) || exprhdl.DeriveHasSubquery(2))
{
return CXform::ExfpNone;
}
return CXform::ExfpHigh;
}
//---------------------------------------------------------------------------
// @function:
// CXformImplementLimit::Transform
//
// @doc:
// Actual transformation
//
//---------------------------------------------------------------------------
void
CXformImplementLimit::Transform(CXformContext *pxfctxt, CXformResult *pxfres,
CExpression *pexpr) const
{
GPOS_ASSERT(nullptr != pxfctxt);
GPOS_ASSERT(FPromising(pxfctxt->Pmp(), this, pexpr));
GPOS_ASSERT(FCheckPattern(pexpr));
CMemoryPool *mp = pxfctxt->Pmp();
// extract components
CLogicalLimit *popLimit = CLogicalLimit::PopConvert(pexpr->Pop());
CExpression *pexprRelational = (*pexpr)[0];
CExpression *pexprScalarStart = (*pexpr)[1];
CExpression *pexprScalarRows = (*pexpr)[2];
COrderSpec *pos = popLimit->Pos();
// addref all components
pexprRelational->AddRef();
pexprScalarStart->AddRef();
pexprScalarRows->AddRef();
popLimit->Pos()->AddRef();
// assemble physical operator
CExpression *pexprLimit = GPOS_NEW(mp) CExpression(
mp,
GPOS_NEW(mp)
CPhysicalLimit(mp, pos, popLimit->FGlobal(), popLimit->FHasCount(),
popLimit->IsTopLimitUnderDMLorCTAS()),
pexprRelational, pexprScalarStart, pexprScalarRows);
// add alternative to results
pxfres->Add(pexprLimit);
}
// EOF
相关信息
相关文章
greenplumn CJoinOrderGreedy 源码
greenplumn CJoinOrderMinCard 源码
greenplumn CSubqueryHandler 源码
0
赞
热门推荐
-
2、 - 优质文章
-
3、 gate.io
-
7、 golang
-
9、 openharmony
-
10、 Vue中input框自动聚焦