greenplumn CReqdProp 源码

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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