greenplumn CRewindabilitySpec 代码
文件路径：/src/backend/gporca/libgpopt/include/gpopt/base/CRewindabilitySpec.h
/---------------------------------------------------------------------------
/ Greenplum Database
/ Copyright (C) 2011 EMC Corp.
/
/ @filename:
/ CRewindabilitySpec.h
/
/ @doc:
/ Rewindability of intermediate query results;
/ Can be used as required or derived property;
/---------------------------------------------------------------------------
#ifndef GPOPT_CRewindabilitySpec_H
#define GPOPT_CRewindabilitySpec_H
#include "gpos/base.h"
#include "gpos/common/CRefCount.h"
#include "gpopt/base/CPropSpec.h"
namespace gpopt
{
using namespace gpos;
/---------------------------------------------------------------------------
/ @class:
/ CRewindabilitySpec
/
/ @doc:
/ Rewindability specification
/
/---------------------------------------------------------------------------
class CRewindabilitySpec : public CPropSpec
{
public:
/ From the perspective of the operator, the enum values mean the
/ following (in required & derived contexts):
/
/ 1. ErtMarkRestore:
/ require:
/ I require my child to be mark-restorable. This is required by MJ of
/ its inner child.
/ derive:
/ I am mark-restorable. (e.g Spool, Sort, Scan)
/ (NB: I cannot derive mark-restorable just because my child is mark-restorable.
/ However, I can derive rewindable.)
/
/ 2. ErtRewindable:
/ require:
/ I require my child to be rewindable. This is required by NLJ of
/ its inner child.
/ derive:
/ I am rewindable. (e.g Spool, Sort, Scan)
/
/ 3. ErtRescannable:
/ require:
/ I require my child to be rescannable, so that I can re-execute
/ the entire subtree if needed. This is required by correlated
/ joins of their inner child.
/ derive:
/ I am not rewindable, but I am rescannable. (e.g TVF containing a
/ volatile function)
/
/ 4. ErtNone
/ require:
/ I do not require my child to be rewindable or rescannable. (e.g
/ Sort that is not on the inner side of a correlated join)
/ derive:
/ I am neither rewindable nor rescannable. (e.g Motions, External
/ table scans)
enum ERewindabilityType
{
ErtMarkRestore, / rewindability with mark & restore support
ErtRewindable, / rewindability of all intermediate query results
ErtRescannable, / not rewindable, but can be reexecuted from scratch
ErtNone, / neither rewindability nor rescannable
ErtSentinel
};
/ From the perspective of the operator, the enum values mean the
/ following (in required & derived contexts):
/
/ 1. EmhtMotion:
/ require:
/ I require my child to handle motion hazard (if necessary)
/ derive:
/ I impose a motion hazard (for example, a streaming spool with a
/ motion underneath it, will derive this)
/
/ 2. EmhtNoMotion:
/ require:
/ Motion hazard handling is unnecessary.
/ derive:
/ I do not impose motion hazard (derived by a rewindable operator
/ without no motion in its subtree or a blocking spool with or
/ without a motion underneath it)
enum EMotionHazardType
{
EmhtMotion, / motion hazard in the tree
EmhtNoMotion, / no motion hazard in the tree
EmhtSentinel
};
private:
/ rewindability support
ERewindabilityType m_rewindability;
/ Motion Hazard
EMotionHazardType m_motion_hazard;
/ Is NL Join
BOOL m_origin_nl_join;
public:
/ ctor
explicit CRewindabilitySpec(ERewindabilityType rewindability_type,
EMotionHazardType motion_hazard,
BOOL origin_nl_join = false);
/ dtor
~CRewindabilitySpec() override;
/ check if rewindability specs match
BOOL Matches(const CRewindabilitySpec *prs) const;
/ check if rewindability spec satisfies a req'd rewindability spec
BOOL FSatisfies(const CRewindabilitySpec *prs) const;
/ append enforcers to dynamic array for the given plan properties
void AppendEnforcers(CMemoryPool *mp, CExpressionHandle &exprhdl,
CReqdPropPlan *prpp, CExpressionArray *pdrgpexpr,
CExpression *pexpr) override;
/ hash function
ULONG HashValue() const override;
/ extract columns used by the rewindability spec
CColRefSet *
PcrsUsed(CMemoryPool *mp) const override
{
/ return an empty set
return GPOS_NEW(mp) CColRefSet(mp);
}
/ property type
EPropSpecType
Epst() const override
{
return EpstRewindability;
}
/ print
IOstream &OsPrint(IOstream &os) const override;
ERewindabilityType
Ert() const
{
return m_rewindability;
}
EMotionHazardType
Emht() const
{
return m_motion_hazard;
}
BOOL
IsOriginNLJoin() const
{
return m_origin_nl_join;
}
BOOL
IsRewindable() const
{
return Ert() == ErtRewindable || Ert() == ErtMarkRestore;
}
BOOL
IsRescannable() const
{
return Ert() == ErtRescannable;
}
BOOL
IsCheckRequired() const
{
return Ert() != ErtNone;
}
BOOL
HasMotionHazard() const
{
return Emht() == EmhtMotion;
}
}; / class CRewindabilitySpec
} / namespace gpopt
#endif / !GPOPT_CRewindabilitySpec_H
/ EOF
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