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) 1996-2010, PostgreSQL Global Development Group
   8  * Portions Copyright (c) 1994, Regents of the University of California
   9  *
  10  * IDENTIFICATION
  11  *        $PostgreSQL: pgsql/src/backend/tcop/dest.c,v 1.76 2010/01/02 16:57:52 momjian Exp $
  12  *
  13  *-------------------------------------------------------------------------
  14  */
  15 /*
  16  *       INTERFACE ROUTINES
  17  *              BeginCommand - initialize the destination at start of command
  18  *              CreateDestReceiver - create tuple receiver object for destination
  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 "commands/copy.h"
  34 #include "executor/executor.h"
  35 #include "executor/functions.h"
  36 #include "executor/tstoreReceiver.h"
  37 #include "libpq/libpq.h"
  38 #include "libpq/pqformat.h"
  39 #include "utils/portal.h"
  40
  41
  42 /* ----------------
  43  *              dummy DestReceiver functions
  44  * ----------------
  45  */
  46 static void
  47 donothingReceive(TupleTableSlot *slot, DestReceiver *self)
  48 {
  49 }
  50
  51 static void
  52 donothingStartup(DestReceiver *self, int operation, TupleDesc typeinfo)
  53 {
  54 }
  55
  56 static void
  57 donothingCleanup(DestReceiver *self)
  58 {
  59         /* this is used for both shutdown and destroy methods */
  60 }
  61
  62 /* ----------------
  63  *              static DestReceiver structs for dest types needing no local state
  64  * ----------------
  65  */
  66 static DestReceiver donothingDR = {
  67         donothingReceive, donothingStartup, donothingCleanup, donothingCleanup,
  68         DestNone
  69 };
  70
  71 static DestReceiver debugtupDR = {
  72         debugtup, debugStartup, donothingCleanup, donothingCleanup,
  73         DestDebug
  74 };
  75
  76 static DestReceiver spi_printtupDR = {
  77         spi_printtup, spi_dest_startup, donothingCleanup, donothingCleanup,
  78         DestSPI
  79 };
  80
  81 /* Globally available receiver for DestNone */
  82 DestReceiver *None_Receiver = &donothingDR;
  83
  84
  85 /* ----------------
  86  *              BeginCommand - initialize the destination at start of command
  87  * ----------------
  88  */
  89 void
  90 BeginCommand(const char *commandTag, CommandDest dest)
  91 {
  92         /* Nothing to do at present */
  93 }
  94
  95 /* ----------------
  96  *              CreateDestReceiver - return appropriate receiver function set for dest
  97  * ----------------
  98  */
  99 DestReceiver *
 100 CreateDestReceiver(CommandDest dest)
 101 {
 102         switch (dest)
 103         {
 104                 case DestRemote:
 105                 case DestRemoteExecute:
 106                         return printtup_create_DR(dest);
 107
 108                 case DestNone:
 109                         return &donothingDR;
 110
 111                 case DestDebug:
 112                         return &debugtupDR;
 113
 114                 case DestSPI:
 115                         return &spi_printtupDR;
 116
 117                 case DestTuplestore:
 118                         return CreateTuplestoreDestReceiver();
 119
 120                 case DestIntoRel:
 121                         return CreateIntoRelDestReceiver();
 122
 123                 case DestCopyOut:
 124                         return CreateCopyDestReceiver();
 125
 126                 case DestSQLFunction:
 127                         return CreateSQLFunctionDestReceiver();
 128         }
 129
 130         /* should never get here */
 131         return &donothingDR;
 132 }
 133
 134 /* ----------------
 135  *              EndCommand - clean up the destination at end of command
 136  * ----------------
 137  */
 138 void
 139 EndCommand(const char *commandTag, CommandDest dest)
 140 {
 141         switch (dest)
 142         {
 143                 case DestRemote:
 144                 case DestRemoteExecute:
 145                         pq_puttextmessage('C', commandTag);
 146                         break;
 147
 148                 case DestNone:
 149                 case DestDebug:
 150                 case DestSPI:
 151                 case DestTuplestore:
 152                 case DestIntoRel:
 153                 case DestCopyOut:
 154                 case DestSQLFunction:
 155                         break;
 156         }
 157 }
 158
 159 /* ----------------
 160  *              NullCommand - tell dest that an empty query string was recognized
 161  *
 162  *              In FE/BE protocol version 1.0, this hack is necessary to support
 163  *              libpq's crufty way of determining whether a multiple-command
 164  *              query string is done.  In protocol 2.0 it's probably not really
 165  *              necessary to distinguish empty queries anymore, but we still do it
 166  *              for backwards compatibility with 1.0.  In protocol 3.0 it has some
 167  *              use again, since it ensures that there will be a recognizable end
 168  *              to the response to an Execute message.
 169  * ----------------
 170  */
 171 void
 172 NullCommand(CommandDest dest)
 173 {
 174         switch (dest)
 175         {
 176                 case DestRemote:
 177                 case DestRemoteExecute:
 178
 179                         /*
 180                          * tell the fe that we saw an empty query string.  In protocols
 181                          * before 3.0 this has a useless empty-string message body.
 182                          */
 183                         if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 3)
 184                                 pq_putemptymessage('I');
 185                         else
 186                                 pq_puttextmessage('I', "");
 187                         break;
 188
 189                 case DestNone:
 190                 case DestDebug:
 191                 case DestSPI:
 192                 case DestTuplestore:
 193                 case DestIntoRel:
 194                 case DestCopyOut:
 195                 case DestSQLFunction:
 196                         break;
 197         }
 198 }
 199
 200 /* ----------------
 201  *              ReadyForQuery - tell dest that we are ready for a new query
 202  *
 203  *              The ReadyForQuery message is sent in protocol versions 2.0 and up
 204  *              so that the FE can tell when we are done processing a query string.
 205  *              In versions 3.0 and up, it also carries a transaction state indicator.
 206  *
 207  *              Note that by flushing the stdio buffer here, we can avoid doing it
 208  *              most other places and thus reduce the number of separate packets sent.
 209  * ----------------
 210  */
 211 void
 212 ReadyForQuery(CommandDest dest)
 213 {
 214         switch (dest)
 215         {
 216                 case DestRemote:
 217                 case DestRemoteExecute:
 218                         if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 3)
 219                         {
 220                                 StringInfoData buf;
 221
 222                                 pq_beginmessage(&buf, 'Z');
 223                                 pq_sendbyte(&buf, TransactionBlockStatusCode());
 224                                 pq_endmessage(&buf);
 225                         }
 226                         else if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 2)
 227                                 pq_putemptymessage('Z');
 228                         /* Flush output at end of cycle in any case. */
 229                         pq_flush();
 230                         break;
 231
 232                 case DestNone:
 233                 case DestDebug:
 234                 case DestSPI:
 235                 case DestTuplestore:
 236                 case DestIntoRel:
 237                 case DestCopyOut:
 238                 case DestSQLFunction:
 239                         break;
 240         }
 241 }