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221 lines
4.8 KiB
C
221 lines
4.8 KiB
C
/*-------------------------------------------------------------------------
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*
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* dest.c
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* support for communication destinations
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*
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*
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* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/tcop/dest.c,v 1.49 2002/06/20 20:29:36 momjian Exp $
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*
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*-------------------------------------------------------------------------
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*/
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/*
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* INTERFACE ROUTINES
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* BeginCommand - initialize the destination at start of command
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* DestToFunction - identify per-tuple processing routines
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* EndCommand - clean up the destination at end of command
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* NullCommand - tell dest that an empty query string was recognized
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* ReadyForQuery - tell dest that we are ready for a new query
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*
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* NOTES
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* These routines do the appropriate work before and after
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* tuples are returned by a query to keep the backend and the
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* "destination" portals synchronized.
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*/
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#include "postgres.h"
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#include "access/printtup.h"
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#include "libpq/libpq.h"
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#include "libpq/pqformat.h"
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/* ----------------
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* dummy DestReceiver functions
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* ----------------
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*/
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static void
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donothingReceive(HeapTuple tuple, TupleDesc typeinfo, DestReceiver *self)
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{
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}
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static void
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donothingSetup(DestReceiver *self, int operation,
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const char *portalName, TupleDesc typeinfo)
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{
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}
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static void
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donothingCleanup(DestReceiver *self)
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{
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}
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/* ----------------
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* static DestReceiver structs for dest types needing no local state
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* ----------------
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*/
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static DestReceiver donothingDR = {
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donothingReceive, donothingSetup, donothingCleanup
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};
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static DestReceiver debugtupDR = {
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debugtup, debugSetup, donothingCleanup
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};
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static DestReceiver spi_printtupDR = {
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spi_printtup, donothingSetup, donothingCleanup
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};
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/* ----------------
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* BeginCommand - initialize the destination at start of command
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* ----------------
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*/
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void
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BeginCommand(const char *commandTag, CommandDest dest)
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{
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/* Nothing to do at present */
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}
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/* ----------------
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* DestToFunction - return appropriate receiver function set for dest
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* ----------------
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*/
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DestReceiver *
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DestToFunction(CommandDest dest)
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{
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switch (dest)
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{
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case Remote:
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return printtup_create_DR(false);
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case RemoteInternal:
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return printtup_create_DR(true);
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case Debug:
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return &debugtupDR;
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case SPI:
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return &spi_printtupDR;
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case None:
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return &donothingDR;
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}
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/* should never get here */
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return &donothingDR;
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}
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/* ----------------
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* EndCommand - clean up the destination at end of command
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* ----------------
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*/
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void
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EndCommand(const char *commandTag, CommandDest dest)
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{
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switch (dest)
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{
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case Remote:
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case RemoteInternal:
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pq_puttextmessage('C', commandTag);
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break;
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case None:
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case Debug:
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case SPI:
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break;
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}
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}
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/*
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* These are necessary to sync communications between fe/be processes doing
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* COPY rel TO stdout
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*
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* or
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*
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* COPY rel FROM stdin
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*
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* NOTE: the message code letters are changed at protocol version 2.0
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* to eliminate possible confusion with data tuple messages.
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*/
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void
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SendCopyBegin(void)
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{
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if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 2)
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pq_putbytes("H", 1); /* new way */
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else
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pq_putbytes("B", 1); /* old way */
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}
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void
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ReceiveCopyBegin(void)
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{
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if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 2)
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pq_putbytes("G", 1); /* new way */
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else
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pq_putbytes("D", 1); /* old way */
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/* We *must* flush here to ensure FE knows it can send. */
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pq_flush();
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}
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/* ----------------
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* NullCommand - tell dest that an empty query string was recognized
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*
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* In FE/BE protocol version 1.0, this hack is necessary to support
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* libpq's crufty way of determining whether a multiple-command
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* query string is done. In protocol 2.0 it's probably not really
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* necessary to distinguish empty queries anymore, but we still do it
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* for backwards compatibility with 1.0.
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* ----------------
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*/
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void
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NullCommand(CommandDest dest)
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{
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switch (dest)
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{
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case RemoteInternal:
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case Remote:
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/*
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* tell the fe that we saw an empty query string
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*/
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pq_putbytes("I", 2); /* note we send I and \0 */
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break;
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case Debug:
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case None:
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default:
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break;
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}
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}
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/* ----------------
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* ReadyForQuery - tell dest that we are ready for a new query
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*
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* The ReadyForQuery message is sent in protocol versions 2.0 and up
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* so that the FE can tell when we are done processing a query string.
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*
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* Note that by flushing the stdio buffer here, we can avoid doing it
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* most other places and thus reduce the number of separate packets sent.
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* ----------------
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*/
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void
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ReadyForQuery(CommandDest dest)
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{
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switch (dest)
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{
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case RemoteInternal:
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case Remote:
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if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 2)
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pq_putbytes("Z", 1);
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/* Flush output at end of cycle in any case. */
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pq_flush();
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break;
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case Debug:
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case None:
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default:
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break;
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}
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}
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