/*------------------------------------------------------------------------- * * dest.h *		Whenever the backend executes a query, the results *		have to go someplace - either to the standard output, *		to a local portal buffer or to a remote portal buffer. * *	  - stdout is the destination only when we are running a *		backend without a postmaster and are returning results *		back to the user. * *	  - a local portal buffer is the destination when a backend *		executes a user-defined function which calls PQexec() or *		PQfn().  In this case, the results are collected into a *		PortalBuffer which the user's function may diddle with. * *	  - a remote portal buffer is the destination when we are *		running a backend with a frontend and the frontend executes *		PQexec() or PQfn().  In this case, the results are sent *		to the frontend via the pq_ functions. * *	  - None is the destination when the system executes *		a query internally.  This is not used now but it may be *		useful for the parallel optimiser/executor. * * dest.c defines three functions that implement destination management: * * BeginCommand: initialize the destination. * DestToFunction: return a pointer to a struct of destination-specific * receiver functions. * EndCommand: clean up the destination when output is complete. * * The DestReceiver object returned by DestToFunction may be a statically * allocated object (for destination types that require no local state) * or can be a palloc'd object that has DestReceiver as its first field * and contains additional fields (see printtup.c for an example).	These * additional fields are then accessible to the DestReceiver functions * by casting the DestReceiver* pointer passed to them. * The palloc'd object is pfree'd by the DestReceiver's cleanup function. * * XXX FIXME: the initialization and cleanup code that currently appears * in-line in BeginCommand and EndCommand probably should be moved out * to routines associated with each destination receiver type. * * Copyright (c) 1994, Regents of the University of California * * $Id: dest.h,v 1.20.2.1 1999/07/30 17:07:20 scrappy Exp $ * *------------------------------------------------------------------------- */#ifndef DEST_H#define DEST_H#include "access/htup.h"#include "access/tupdesc.h"/* ---------------- *		CommandDest is a simplistic means of identifying the desired *		destination.  Someday this will probably need to be improved. * ---------------- */typedef enum{	None,						/* results are discarded */	Debug,						/* results go to debugging output */	Local,						/* results go in local portal buffer */	Remote,						/* results sent to frontend process */	RemoteInternal,				/* results sent to frontend process in								 * internal (binary) form */	SPI							/* results sent to SPI manager */} CommandDest;/* ---------------- *		DestReceiver is a base type for destination-specific local state. *		In the simplest cases, there is no state info, just the function *		pointers that the executor must call. * ---------------- */typedef struct _DestReceiver DestReceiver;struct _DestReceiver{	/* Called for each tuple to be output: */	void		(*receiveTuple) (HeapTuple tuple, TupleDesc typeinfo,											 DestReceiver *self);	/* Initialization and teardown: */	void		(*setup) (DestReceiver *self, TupleDesc typeinfo);	void		(*cleanup) (DestReceiver *self);	/* Private fields might appear beyond this point... */};/* The primary destination management functions */extern void BeginCommand(char *pname, int operation, TupleDesc attinfo,			 bool isIntoRel, bool isIntoPortal, char *tag,			 CommandDest dest);extern DestReceiver *DestToFunction(CommandDest dest);extern void EndCommand(char *commandTag, CommandDest dest);/* Additional functions that go with destination management, more or less. */extern void SendCopyBegin(void);extern void ReceiveCopyBegin(void);extern void NullCommand(CommandDest dest);extern void ReadyForQuery(CommandDest dest);extern void UpdateCommandInfo(int operation, Oid lastoid, uint32 tuples);#endif	 /* DEST_H */