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/*-------------------------------------------------------------------------
*
* dest.c
* support for communication destinations
*
*
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/tcop/dest.c,v 1.49.2.1 2003/01/21 22:06:36 tgl Exp $
*
*-------------------------------------------------------------------------
*/
/*
* INTERFACE ROUTINES
* BeginCommand - initialize the destination at start of command
* DestToFunction - identify per-tuple processing routines
* EndCommand - clean up the destination at end of command
* NullCommand - tell dest that an empty query string was recognized
* ReadyForQuery - tell dest that we are ready for a new query
*
* NOTES
* These routines do the appropriate work before and after
* tuples are returned by a query to keep the backend and the
* "destination" portals synchronized.
*/
#include "postgres.h"
#include "access/printtup.h"
#include "libpq/libpq.h"
#include "libpq/pqformat.h"
/* ----------------
* dummy DestReceiver functions
* ----------------
*/
static void
donothingReceive(HeapTuple tuple, TupleDesc typeinfo, DestReceiver *self)
{
}
static void
donothingSetup(DestReceiver *self, int operation,
const char *portalName, TupleDesc typeinfo)
{
}
static void
donothingCleanup(DestReceiver *self)
{
}
/* ----------------
* static DestReceiver structs for dest types needing no local state
* ----------------
*/
static DestReceiver donothingDR = {
donothingReceive, donothingSetup, donothingCleanup
};
static DestReceiver debugtupDR = {
debugtup, debugSetup, donothingCleanup
};
static DestReceiver spi_printtupDR = {
spi_printtup, spi_dest_setup, donothingCleanup
};
/* ----------------
* BeginCommand - initialize the destination at start of command
* ----------------
*/
void
BeginCommand(const char *commandTag, CommandDest dest)
{
/* Nothing to do at present */
}
/* ----------------
* DestToFunction - return appropriate receiver function set for dest
* ----------------
*/
DestReceiver *
DestToFunction(CommandDest dest)
{
switch (dest)
{
case Remote:
return printtup_create_DR(false);
case RemoteInternal:
return printtup_create_DR(true);
case Debug:
return &debugtupDR;
case SPI:
return &spi_printtupDR;
case None:
return &donothingDR;
}
/* should never get here */
return &donothingDR;
}
/* ----------------
* EndCommand - clean up the destination at end of command
* ----------------
*/
void
EndCommand(const char *commandTag, CommandDest dest)
{
switch (dest)
{
case Remote:
case RemoteInternal:
pq_puttextmessage('C', commandTag);
break;
case None:
case Debug:
case SPI:
break;
}
}
/*
* These are necessary to sync communications between fe/be processes doing
* COPY rel TO stdout
*
* or
*
* COPY rel FROM stdin
*
* NOTE: the message code letters are changed at protocol version 2.0
* to eliminate possible confusion with data tuple messages.
*/
void
SendCopyBegin(void)
{
if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 2)
pq_putbytes("H", 1); /* new way */
else
pq_putbytes("B", 1); /* old way */
}
void
ReceiveCopyBegin(void)
{
if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 2)
pq_putbytes("G", 1); /* new way */
else
pq_putbytes("D", 1); /* old way */
/* We *must* flush here to ensure FE knows it can send. */
pq_flush();
}
/* ----------------
* NullCommand - tell dest that an empty query string was recognized
*
* In FE/BE protocol version 1.0, this hack is necessary to support
* libpq's crufty way of determining whether a multiple-command
* query string is done. In protocol 2.0 it's probably not really
* necessary to distinguish empty queries anymore, but we still do it
* for backwards compatibility with 1.0.
* ----------------
*/
void
NullCommand(CommandDest dest)
{
switch (dest)
{
case RemoteInternal:
case Remote:
/*
* tell the fe that we saw an empty query string
*/
pq_putbytes("I", 2); /* note we send I and \0 */
break;
case Debug:
case None:
default:
break;
}
}
/* ----------------
* ReadyForQuery - tell dest that we are ready for a new query
*
* The ReadyForQuery message is sent in protocol versions 2.0 and up
* so that the FE can tell when we are done processing a query string.
*
* Note that by flushing the stdio buffer here, we can avoid doing it
* most other places and thus reduce the number of separate packets sent.
* ----------------
*/
void
ReadyForQuery(CommandDest dest)
{
switch (dest)
{
case RemoteInternal:
case Remote:
if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 2)
pq_putbytes("Z", 1);
/* Flush output at end of cycle in any case. */
pq_flush();
break;
case Debug:
case None:
default:
break;
}
}
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