//---------------------------------------------------------------------------
//	Greenplum Database
//	Copyright (C) 2011 EMC Corp.
//
//	@filename:
//		IMDFunction.h
//
//	@doc:
//		Interface for functions in the metadata cache
//---------------------------------------------------------------------------



#ifndef GPMD_IMDFunction_H
#define GPMD_IMDFunction_H

#include "gpos/base.h"

#include "naucrates/md/IMDCacheObject.h"

namespace gpmd
{
using namespace gpos;


//---------------------------------------------------------------------------
//	@class:
//		IMDFunction
//
//	@doc:
//		Interface for functions in the metadata cache
//
//---------------------------------------------------------------------------
class IMDFunction : public IMDCacheObject
{
public:
	// function stability property
	enum EFuncStbl
	{
		EfsImmutable, /* never changes for given input */
		EfsStable,	  /* does not change within a scan */
		EfsVolatile,  /* can change even within a scan */
		EfsSentinel
	};

	// object type
	Emdtype
	MDType() const override
	{
		return EmdtFunc;
	}

	// does function return NULL on NULL input
	virtual BOOL IsStrict() const = 0;

	// does function preserve NDVs of input (for cardinality estimation)
	virtual BOOL IsNDVPreserving() const = 0;

	// does function return a set of values
	virtual BOOL ReturnsSet() const = 0;

	// is this function allowed for Partition selection
	virtual BOOL IsAllowedForPS() const = 0;

	// function stability
	virtual EFuncStbl GetFuncStability() const = 0;

	// result type
	virtual IMDId *GetResultTypeMdid() const = 0;

	// output argument types
	virtual IMdIdArray *OutputArgTypesMdidArray() const = 0;
};

}  // namespace gpmd

#endif	// !GPMD_IMDFunction_H

// EOF