granicus.if.org Git - postgresql/blob - src/backend/tcop/dest.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * dest.c
   4  *        support for communication destinations
   5  *
   6  *
   7  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
   8  * Portions Copyright (c) 1994, Regents of the University of California
   9  *
  10  * IDENTIFICATION
  11  *        $Header: /cvsroot/pgsql/src/backend/tcop/dest.c,v 1.56 2003/05/06 00:20:33 tgl Exp $
  12  *
  13  *-------------------------------------------------------------------------
  14  */
  15 /*
  16  *       INTERFACE ROUTINES
  17  *              BeginCommand - initialize the destination at start of command
  18  *              DestToFunction - identify per-tuple processing routines
  19  *              EndCommand - clean up the destination at end of command
  20  *              NullCommand - tell dest that an empty query string was recognized
  21  *              ReadyForQuery - tell dest that we are ready for a new query
  22  *
  23  *       NOTES
  24  *              These routines do the appropriate work before and after
  25  *              tuples are returned by a query to keep the backend and the
  26  *              "destination" portals synchronized.
  27  */
  28
  29 #include "postgres.h"
  30
  31 #include "access/printtup.h"
  32 #include "access/xact.h"
  33 #include "executor/tstoreReceiver.h"
  34 #include "libpq/libpq.h"
  35 #include "libpq/pqformat.h"
  36
  37
  38 /* ----------------
  39  *              dummy DestReceiver functions
  40  * ----------------
  41  */
  42 static void
  43 donothingReceive(HeapTuple tuple, TupleDesc typeinfo, DestReceiver *self)
  44 {
  45 }
  46
  47 static void
  48 donothingSetup(DestReceiver *self, int operation,
  49                            const char *portalName, TupleDesc typeinfo, List *targetlist)
  50 {
  51 }
  52
  53 static void
  54 donothingCleanup(DestReceiver *self)
  55 {
  56 }
  57
  58 /* ----------------
  59  *              static DestReceiver structs for dest types needing no local state
  60  * ----------------
  61  */
  62 static DestReceiver donothingDR = {
  63         donothingReceive, donothingSetup, donothingCleanup
  64 };
  65
  66 static DestReceiver debugtupDR = {
  67         debugtup, debugSetup, donothingCleanup
  68 };
  69
  70 static DestReceiver spi_printtupDR = {
  71         spi_printtup, spi_dest_setup, donothingCleanup
  72 };
  73
  74 /* ----------------
  75  *              BeginCommand - initialize the destination at start of command
  76  * ----------------
  77  */
  78 void
  79 BeginCommand(const char *commandTag, CommandDest dest)
  80 {
  81         /* Nothing to do at present */
  82 }
  83
  84 /* ----------------
  85  *              DestToFunction - return appropriate receiver function set for dest
  86  * ----------------
  87  */
  88 DestReceiver *
  89 DestToFunction(CommandDest dest)
  90 {
  91         switch (dest)
  92         {
  93                 case Remote:
  94                         return printtup_create_DR(false, true);
  95
  96                 case RemoteInternal:
  97                         return printtup_create_DR(true, true);
  98
  99                 case RemoteExecute:
 100                         /* like Remote, but suppress output of T message */
 101                         return printtup_create_DR(false, false);
 102
 103                 case RemoteExecuteInternal:
 104                         return printtup_create_DR(true, false);
 105
 106                 case None:
 107                         return &donothingDR;
 108
 109                 case Debug:
 110                         return &debugtupDR;
 111
 112                 case SPI:
 113                         return &spi_printtupDR;
 114
 115                 case Tuplestore:
 116                         return tstoreReceiverCreateDR();
 117         }
 118
 119         /* should never get here */
 120         return &donothingDR;
 121 }
 122
 123 /* ----------------
 124  *              EndCommand - clean up the destination at end of command
 125  * ----------------
 126  */
 127 void
 128 EndCommand(const char *commandTag, CommandDest dest)
 129 {
 130         switch (dest)
 131         {
 132                 case Remote:
 133                 case RemoteInternal:
 134                 case RemoteExecute:
 135                 case RemoteExecuteInternal:
 136                         pq_puttextmessage('C', commandTag);
 137                         break;
 138
 139                 case None:
 140                 case Debug:
 141                 case SPI:
 142                 case Tuplestore:
 143                         break;
 144         }
 145 }
 146
 147 /* ----------------
 148  *              NullCommand - tell dest that an empty query string was recognized
 149  *
 150  *              In FE/BE protocol version 1.0, this hack is necessary to support
 151  *              libpq's crufty way of determining whether a multiple-command
 152  *              query string is done.  In protocol 2.0 it's probably not really
 153  *              necessary to distinguish empty queries anymore, but we still do it
 154  *              for backwards compatibility with 1.0.  In protocol 3.0 it has some
 155  *              use again, since it ensures that there will be a recognizable end
 156  *              to the response to an Execute message.
 157  * ----------------
 158  */
 159 void
 160 NullCommand(CommandDest dest)
 161 {
 162         switch (dest)
 163         {
 164                 case Remote:
 165                 case RemoteInternal:
 166                 case RemoteExecute:
 167                 case RemoteExecuteInternal:
 168
 169                         /*
 170                          * tell the fe that we saw an empty query string.  In protocols
 171                          * before 3.0 this has a useless empty-string message body.
 172                          */
 173                         if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 3)
 174                                 pq_putemptymessage('I');
 175                         else
 176                                 pq_puttextmessage('I', "");
 177                         break;
 178
 179                 case None:
 180                 case Debug:
 181                 case SPI:
 182                 case Tuplestore:
 183                         break;
 184         }
 185 }
 186
 187 /* ----------------
 188  *              ReadyForQuery - tell dest that we are ready for a new query
 189  *
 190  *              The ReadyForQuery message is sent in protocol versions 2.0 and up
 191  *              so that the FE can tell when we are done processing a query string.
 192  *              In versions 3.0 and up, it also carries a transaction state indicator.
 193  *
 194  *              Note that by flushing the stdio buffer here, we can avoid doing it
 195  *              most other places and thus reduce the number of separate packets sent.
 196  * ----------------
 197  */
 198 void
 199 ReadyForQuery(CommandDest dest)
 200 {
 201         switch (dest)
 202         {
 203                 case Remote:
 204                 case RemoteInternal:
 205                 case RemoteExecute:
 206                 case RemoteExecuteInternal:
 207                         if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 3)
 208                         {
 209                                 StringInfoData buf;
 210
 211                                 pq_beginmessage(&buf, 'Z');
 212                                 pq_sendbyte(&buf, TransactionBlockStatusCode());
 213                                 pq_endmessage(&buf);
 214                         }
 215                         else if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 2)
 216                                 pq_putemptymessage('Z');
 217                         /* Flush output at end of cycle in any case. */
 218                         pq_flush();
 219                         break;
 220
 221                 case None:
 222                 case Debug:
 223                 case SPI:
 224                 case Tuplestore:
 225                         break;
 226         }
 227 }