greenplumn CLogicalLimit 代码
文件路径：/src/backend/gporca/libgpopt/include/gpopt/operators/CLogicalLimit.h
/---------------------------------------------------------------------------
/ Greenplum Database
/ Copyright (C) 2011 EMC Corp.
/
/ @filename:
/ CLogicalLimit.h
/
/ @doc:
/ Limit operator
/---------------------------------------------------------------------------
#ifndef GPOPT_CLogicalLimit_H
#define GPOPT_CLogicalLimit_H
#include "gpos/base.h"
#include "gpopt/base/COrderSpec.h"
#include "gpopt/operators/CLogical.h"
#include "naucrates/md/IMDId.h"
namespace gpopt
{
/---------------------------------------------------------------------------
/ @class:
/ CLogicalLimit
/
/ @doc:
/ Limit operator;
/ Scalar children compute (1) offset of start row, (2) number of rows
/
/---------------------------------------------------------------------------
class CLogicalLimit : public CLogical
{
private:
/ required sort order
COrderSpec *m_pos;
/ global limit
BOOL m_fGlobal;
/ does limit specify a number of rows?
BOOL m_fHasCount;
/ the limit must be kept, even if it has no offset, nor count
BOOL m_top_limit_under_dml;
public:
CLogicalLimit(const CLogicalLimit &) = delete;
/ ctors
explicit CLogicalLimit(CMemoryPool *mp);
CLogicalLimit(CMemoryPool *mp, COrderSpec *pos, BOOL fGlobal,
BOOL fHasCount, BOOL fTopLimitUnderDML);
/ dtor
~CLogicalLimit() override;
/ ident accessors
EOperatorId
Eopid() const override
{
return EopLogicalLimit;
}
const CHAR *
SzId() const override
{
return "CLogicalLimit";
}
/ order spec
COrderSpec *
Pos() const
{
return m_pos;
}
/ global limit
BOOL
FGlobal() const
{
return m_fGlobal;
}
/ does limit specify a number of rows
BOOL
FHasCount() const
{
return m_fHasCount;
}
/ must the limit be always kept
BOOL
IsTopLimitUnderDMLorCTAS() const
{
return m_top_limit_under_dml;
}
/ match function
BOOL Matches(COperator *) const override;
/ sensitivity to order of inputs
BOOL
FInputOrderSensitive() const override
{
return true;
}
/ hash function
ULONG HashValue() const override;
/ return a copy of the operator with remapped columns
COperator *PopCopyWithRemappedColumns(CMemoryPool *mp,
UlongToColRefMap *colref_mapping,
BOOL must_exist) override;
/ print
IOstream &OsPrint(IOstream &os) const override;
/-------------------------------------------------------------------------------------
/ Derived Relational Properties
/-------------------------------------------------------------------------------------
/ derive output columns
CColRefSet *DeriveOutputColumns(CMemoryPool *mp,
CExpressionHandle &exprhdl) override;
/ derive outer references
CColRefSet *DeriveOuterReferences(CMemoryPool *mp,
CExpressionHandle &exprhdl) override;
/ dervive keys
CKeyCollection *DeriveKeyCollection(
CMemoryPool *mp, CExpressionHandle &exprhdl) const override;
/ derive max card
CMaxCard DeriveMaxCard(CMemoryPool *mp,
CExpressionHandle &exprhdl) const override;
/ derive partition consumer info
CPartInfo *
DerivePartitionInfo(CMemoryPool *, / mp
CExpressionHandle &exprhdl) const override
{
return PpartinfoPassThruOuter(exprhdl);
}
/ derive constraint property
CPropConstraint *
DerivePropertyConstraint(CMemoryPool *, /mp,
CExpressionHandle &exprhdl) const override
{
return PpcDeriveConstraintPassThru(exprhdl, 0 /*ulChild*/);
}
/-------------------------------------------------------------------------------------
/ Required Relational Properties
/-------------------------------------------------------------------------------------
/ compute required stat columns of the n-th child
CColRefSet *PcrsStat(CMemoryPool *mp, CExpressionHandle &exprhdl,
CColRefSet *pcrsInput,
ULONG child_index) const override;
/-------------------------------------------------------------------------------------
/ Transformations
/-------------------------------------------------------------------------------------
/ candidate set of xforms
CXformSet *PxfsCandidates(CMemoryPool *) const override;
/ stat promise
EStatPromise
Esp(CExpressionHandle &) const override
{
return CLogical::EspHigh;
}
/ derive statistics
IStatistics *PstatsDerive(CMemoryPool *mp, CExpressionHandle &exprhdl,
IStatisticsArray *stats_ctxt) const override;
/-------------------------------------------------------------------------------------
/-------------------------------------------------------------------------------------
/-------------------------------------------------------------------------------------
/ conversion function
static CLogicalLimit *
PopConvert(COperator *pop)
{
GPOS_ASSERT(nullptr != pop);
GPOS_ASSERT(EopLogicalLimit == pop->Eopid());
return dynamic_cast<CLogicalLimit *>(pop);
}
}; / class CLogicalLimit
} / namespace gpopt
#endif / !GPOPT_CLogicalLimit_H
/ EOF
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