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dest.c
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1 /*-------------------------------------------------------------------------
2  *
3  * dest.c
4  * support for communication destinations
5  *
6  *
7  * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
8  * Portions Copyright (c) 1994, Regents of the University of California
9  *
10  * IDENTIFICATION
11  * src/backend/tcop/dest.c
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/printsimple.h"
32 #include "access/printtup.h"
33 #include "access/xact.h"
34 #include "commands/copy.h"
35 #include "commands/createas.h"
36 #include "commands/explain.h"
37 #include "commands/matview.h"
38 #include "executor/functions.h"
39 #include "executor/tqueue.h"
41 #include "libpq/libpq.h"
42 #include "libpq/pqformat.h"
43 
44 
45 /* ----------------
46  * dummy DestReceiver functions
47  * ----------------
48  */
49 static bool
51 {
52  return true;
53 }
54 
55 static void
56 donothingStartup(DestReceiver *self, int operation, TupleDesc typeinfo)
57 {
58 }
59 
60 static void
62 {
63  /* this is used for both shutdown and destroy methods */
64 }
65 
66 /* ----------------
67  * static DestReceiver structs for dest types needing no local state
68  * ----------------
69  */
70 static const DestReceiver donothingDR = {
72  DestNone
73 };
74 
75 static const DestReceiver debugtupDR = {
77  DestDebug
78 };
79 
80 static const DestReceiver printsimpleDR = {
83 };
84 
85 static const DestReceiver spi_printtupDR = {
87  DestSPI
88 };
89 
90 /*
91  * Globally available receiver for DestNone.
92  *
93  * It's ok to cast the constness away as any modification of the none receiver
94  * would be a bug (which gets easier to catch this way).
95  */
97 
98 /* ----------------
99  * BeginCommand - initialize the destination at start of command
100  * ----------------
101  */
102 void
104 {
105  /* Nothing to do at present */
106 }
107 
108 /* ----------------
109  * CreateDestReceiver - return appropriate receiver function set for dest
110  * ----------------
111  */
112 DestReceiver *
114 {
115  /*
116  * It's ok to cast the constness away as any modification of the none
117  * receiver would be a bug (which gets easier to catch this way).
118  */
119 
120  switch (dest)
121  {
122  case DestRemote:
123  case DestRemoteExecute:
124  return printtup_create_DR(dest);
125 
126  case DestRemoteSimple:
128 
129  case DestNone:
130  return unconstify(DestReceiver *, &donothingDR);
131 
132  case DestDebug:
133  return unconstify(DestReceiver *, &debugtupDR);
134 
135  case DestSPI:
137 
138  case DestTuplestore:
140 
141  case DestIntoRel:
142  return CreateIntoRelDestReceiver(NULL);
143 
144  case DestCopyOut:
145  return CreateCopyDestReceiver();
146 
147  case DestSQLFunction:
149 
150  case DestTransientRel:
152 
153  case DestTupleQueue:
154  return CreateTupleQueueDestReceiver(NULL);
155 
158  }
159 
160  /* should never get here */
161  pg_unreachable();
162 }
163 
164 /* ----------------
165  * EndCommand - clean up the destination at end of command
166  * ----------------
167  */
168 void
169 EndCommand(const QueryCompletion *qc, CommandDest dest, bool force_undecorated_output)
170 {
171  char completionTag[COMPLETION_TAG_BUFSIZE];
172  Size len;
173 
174  switch (dest)
175  {
176  case DestRemote:
177  case DestRemoteExecute:
178  case DestRemoteSimple:
179 
180  len = BuildQueryCompletionString(completionTag, qc,
181  force_undecorated_output);
182  pq_putmessage(PqMsg_CommandComplete, completionTag, len + 1);
183 
184  case DestNone:
185  case DestDebug:
186  case DestSPI:
187  case DestTuplestore:
188  case DestIntoRel:
189  case DestCopyOut:
190  case DestSQLFunction:
191  case DestTransientRel:
192  case DestTupleQueue:
194  break;
195  }
196 }
197 
198 /* ----------------
199  * EndReplicationCommand - stripped down version of EndCommand
200  *
201  * For use by replication commands.
202  * ----------------
203  */
204 void
205 EndReplicationCommand(const char *commandTag)
206 {
207  pq_putmessage(PqMsg_CommandComplete, commandTag, strlen(commandTag) + 1);
208 }
209 
210 /* ----------------
211  * NullCommand - tell dest that an empty query string was recognized
212  *
213  * This ensures that there will be a recognizable end to the response
214  * to an Execute message in the extended query protocol.
215  * ----------------
216  */
217 void
219 {
220  switch (dest)
221  {
222  case DestRemote:
223  case DestRemoteExecute:
224  case DestRemoteSimple:
225 
226  /* Tell the FE that we saw an empty query string */
228  break;
229 
230  case DestNone:
231  case DestDebug:
232  case DestSPI:
233  case DestTuplestore:
234  case DestIntoRel:
235  case DestCopyOut:
236  case DestSQLFunction:
237  case DestTransientRel:
238  case DestTupleQueue:
240  break;
241  }
242 }
243 
244 /* ----------------
245  * ReadyForQuery - tell dest that we are ready for a new query
246  *
247  * The ReadyForQuery message is sent so that the FE can tell when
248  * we are done processing a query string.
249  * In versions 3.0 and up, it also carries a transaction state indicator.
250  *
251  * Note that by flushing the stdio buffer here, we can avoid doing it
252  * most other places and thus reduce the number of separate packets sent.
253  * ----------------
254  */
255 void
257 {
258  switch (dest)
259  {
260  case DestRemote:
261  case DestRemoteExecute:
262  case DestRemoteSimple:
263  {
265 
268  pq_endmessage(&buf);
269  }
270  /* Flush output at end of cycle in any case. */
271  pq_flush();
272  break;
273 
274  case DestNone:
275  case DestDebug:
276  case DestSPI:
277  case DestTuplestore:
278  case DestIntoRel:
279  case DestCopyOut:
280  case DestSQLFunction:
281  case DestTransientRel:
282  case DestTupleQueue:
284  break;
285  }
286 }
#define unconstify(underlying_type, expr)
Definition: c.h:1245
#define pg_unreachable()
Definition: c.h:296
size_t Size
Definition: c.h:605
Size BuildQueryCompletionString(char *buff, const QueryCompletion *qc, bool nameonly)
Definition: cmdtag.c:121
#define COMPLETION_TAG_BUFSIZE
Definition: cmdtag.h:17
CommandTag
Definition: cmdtag.h:23
DestReceiver * CreateCopyDestReceiver(void)
Definition: copyto.c:1267
DestReceiver * CreateIntoRelDestReceiver(IntoClause *intoClause)
Definition: createas.c:435
void EndCommand(const QueryCompletion *qc, CommandDest dest, bool force_undecorated_output)
Definition: dest.c:169
static const DestReceiver spi_printtupDR
Definition: dest.c:85
static void donothingStartup(DestReceiver *self, int operation, TupleDesc typeinfo)
Definition: dest.c:56
static void donothingCleanup(DestReceiver *self)
Definition: dest.c:61
void BeginCommand(CommandTag commandTag, CommandDest dest)
Definition: dest.c:103
static const DestReceiver debugtupDR
Definition: dest.c:75
static const DestReceiver donothingDR
Definition: dest.c:70
void ReadyForQuery(CommandDest dest)
Definition: dest.c:256
static bool donothingReceive(TupleTableSlot *slot, DestReceiver *self)
Definition: dest.c:50
void EndReplicationCommand(const char *commandTag)
Definition: dest.c:205
DestReceiver * None_Receiver
Definition: dest.c:96
static const DestReceiver printsimpleDR
Definition: dest.c:80
DestReceiver * CreateDestReceiver(CommandDest dest)
Definition: dest.c:113
void NullCommand(CommandDest dest)
Definition: dest.c:218
CommandDest
Definition: dest.h:86
@ DestSQLFunction
Definition: dest.h:96
@ DestTupleQueue
Definition: dest.h:98
@ DestTuplestore
Definition: dest.h:93
@ DestRemote
Definition: dest.h:89
@ DestDebug
Definition: dest.h:88
@ DestExplainSerialize
Definition: dest.h:99
@ DestRemoteSimple
Definition: dest.h:91
@ DestCopyOut
Definition: dest.h:95
@ DestTransientRel
Definition: dest.h:97
@ DestSPI
Definition: dest.h:92
@ DestIntoRel
Definition: dest.h:94
@ DestRemoteExecute
Definition: dest.h:90
@ DestNone
Definition: dest.h:87
DestReceiver * CreateExplainSerializeDestReceiver(ExplainState *es)
Definition: explain.c:5549
DestReceiver * CreateSQLFunctionDestReceiver(void)
Definition: functions.c:2062
#define pq_flush()
Definition: libpq.h:46
#define pq_putmessage(msgtype, s, len)
Definition: libpq.h:49
DestReceiver * CreateTransientRelDestReceiver(Oid transientoid)
Definition: matview.c:432
const void size_t len
static char * buf
Definition: pg_test_fsync.c:73
#define InvalidOid
Definition: postgres_ext.h:36
void pq_putemptymessage(char msgtype)
Definition: pqformat.c:388
void pq_endmessage(StringInfo buf)
Definition: pqformat.c:296
void pq_beginmessage(StringInfo buf, char msgtype)
Definition: pqformat.c:88
static void pq_sendbyte(StringInfo buf, uint8 byt)
Definition: pqformat.h:160
void printsimple_startup(DestReceiver *self, int operation, TupleDesc tupdesc)
Definition: printsimple.c:31
bool printsimple(TupleTableSlot *slot, DestReceiver *self)
Definition: printsimple.c:59
bool debugtup(TupleTableSlot *slot, DestReceiver *self)
Definition: printtup.c:461
void debugStartup(DestReceiver *self, int operation, TupleDesc typeinfo)
Definition: printtup.c:443
DestReceiver * printtup_create_DR(CommandDest dest)
Definition: printtup.c:70
#define PqMsg_ReadyForQuery
Definition: protocol.h:55
#define PqMsg_EmptyQueryResponse
Definition: protocol.h:47
#define PqMsg_CommandComplete
Definition: protocol.h:42
bool spi_printtup(TupleTableSlot *slot, DestReceiver *self)
Definition: spi.c:2166
void spi_dest_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
Definition: spi.c:2118
DestReceiver * CreateTupleQueueDestReceiver(shm_mq_handle *handle)
Definition: tqueue.c:119
DestReceiver * CreateTuplestoreDestReceiver(void)
char TransactionBlockStatusCode(void)
Definition: xact.c:4960