greenplumn CReqdProp 代码
文件路径：/src/backend/gporca/libgpopt/include/gpopt/base/CReqdProp.h
/---------------------------------------------------------------------------
/ Greenplum Database
/ Copyright (C) 2011 EMC Corp.
/
/ @filename:
/ CReqdProp.h
/
/ @doc:
/ Base class for all required properties
/---------------------------------------------------------------------------
#ifndef GPOPT_CReqdProp_H
#define GPOPT_CReqdProp_H
#include "gpos/base.h"
#include "gpos/common/CDynamicPtrArray.h"
#include "gpos/common/CRefCount.h"
#include "gpos/common/DbgPrintMixin.h"
#include "gpopt/base/CDrvdProp.h"
namespace gpopt
{
using namespace gpos;
/ forward declarations
class CExpressionHandle;
class COperator;
class CReqdProp;
/ dynamic array for required properties
using CReqdPropArray = CDynamicPtrArray<CReqdProp, CleanupRelease>;
/---------------------------------------------------------------------------
/ @class:
/ CReqdProp
/
/ @doc:
/ Abstract base class for all required properties. Individual property
/ components are added separately. CReqdProp is memory pool-agnostic.
/
/ All derived property classes implement a pure virtual function
/ CReqdProp::Compute(). This function is responsible for filling in the
/ different properties in the property container.
/
/ During query optimization, the optimizer looks for a physical plan that
/ satisfies a number of requirements. These requirements may be specified
/ on the query level such as an ORDER BY clause that specifies a required
/ sort order to be satisfied by query results (see Query Context
/ section). Alternatively, the requirements may be triggered when
/ optimizing a plan subtree. For example, a Hash Join operator may
/ require its children to have hash distributions aligned with the
/ columns mentioned in join condition.
/
/ In either case, each operator receives requirements from the parent and
/ combines these requirements with local requirements to generate new
/ requirements (which may be empty) from each of its children.
/ Recursively, this operation keeps going until the requirements are
/ propagated to all nodes in a given plan in a top-down fashion. The
/ initial set of requirements from the query are constructed in
/ CQueryContext::PqcGenerate().
/
/ Thus each operator needs to implement a virtual requirement function
/ to be called by this mechanism. For example, CPhysical::PcrsChildReqd()
/ is used to compute the required columns by a given operator from its
/ children.
/
/---------------------------------------------------------------------------
class CReqdProp : public CRefCount, public DbgPrintMixin<CReqdProp>
{
public:
/ types of required properties
enum EPropType
{
EptRelational,
EptPlan,
EptSentinel
};
private:
public:
CReqdProp(const CReqdProp &) = delete;
/ ctor
CReqdProp();
/ dtor
~CReqdProp() override;
/ is it a relational property?
virtual BOOL
FRelational() const
{
return false;
}
/ is it a plan property?
virtual BOOL
FPlan() const
{
return false;
}
/ required properties computation function
virtual void Compute(CMemoryPool *mp, CExpressionHandle &exprhdl,
CReqdProp *prpInput, ULONG child_index,
CDrvdPropArray *pdrgpdpCtxt, ULONG ulOptReq) = 0;
virtual gpos::IOstream &OsPrint(gpos::IOstream &os) const = 0;
}; / class CReqdProp
/ shorthand for printing
inline IOstream &
operator<<(IOstream &os, const CReqdProp &reqdprop)
{
return reqdprop.OsPrint(os);
}
} / namespace gpopt
#endif / !GPOPT_CReqdProp_H
/ EOF
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