1 /*-------------------------------------------------------------------------
2 *
3 * dest.c
4 * support for communication destinations
5 *
6 *
7 * Portions Copyright (c) 1996-2020, 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/matview.h"
37 #include "executor/functions.h"
38 #include "executor/tqueue.h"
39 #include "executor/tstoreReceiver.h"
40 #include "libpq/libpq.h"
41 #include "libpq/pqformat.h"
42 #include "utils/portal.h"
43
44
45 /* ----------------
46 * dummy DestReceiver functions
47 * ----------------
48 */
49 static bool
donothingReceive(TupleTableSlot * slot,DestReceiver * self)50 donothingReceive(TupleTableSlot *slot, DestReceiver *self)
51 {
52 return true;
53 }
54
55 static void
donothingStartup(DestReceiver * self,int operation,TupleDesc typeinfo)56 donothingStartup(DestReceiver *self, int operation, TupleDesc typeinfo)
57 {
58 }
59
60 static void
donothingCleanup(DestReceiver * self)61 donothingCleanup(DestReceiver *self)
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 = {
71 donothingReceive, donothingStartup, donothingCleanup, donothingCleanup,
72 DestNone
73 };
74
75 static const DestReceiver debugtupDR = {
76 debugtup, debugStartup, donothingCleanup, donothingCleanup,
77 DestDebug
78 };
79
80 static const DestReceiver printsimpleDR = {
81 printsimple, printsimple_startup, donothingCleanup, donothingCleanup,
82 DestRemoteSimple
83 };
84
85 static const DestReceiver spi_printtupDR = {
86 spi_printtup, spi_dest_startup, donothingCleanup, donothingCleanup,
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 */
96 DestReceiver *None_Receiver = (DestReceiver *) &donothingDR;
97
98 /* ----------------
99 * BeginCommand - initialize the destination at start of command
100 * ----------------
101 */
102 void
BeginCommand(CommandTag commandTag,CommandDest dest)103 BeginCommand(CommandTag commandTag, CommandDest dest)
104 {
105 /* Nothing to do at present */
106 }
107
108 /* ----------------
109 * CreateDestReceiver - return appropriate receiver function set for dest
110 * ----------------
111 */
112 DestReceiver *
CreateDestReceiver(CommandDest dest)113 CreateDestReceiver(CommandDest dest)
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:
127 return unconstify(DestReceiver *, &printsimpleDR);
128
129 case DestNone:
130 return unconstify(DestReceiver *, &donothingDR);
131
132 case DestDebug:
133 return unconstify(DestReceiver *, &debugtupDR);
134
135 case DestSPI:
136 return unconstify(DestReceiver *, &spi_printtupDR);
137
138 case DestTuplestore:
139 return CreateTuplestoreDestReceiver();
140
141 case DestIntoRel:
142 return CreateIntoRelDestReceiver(NULL);
143
144 case DestCopyOut:
145 return CreateCopyDestReceiver();
146
147 case DestSQLFunction:
148 return CreateSQLFunctionDestReceiver();
149
150 case DestTransientRel:
151 return CreateTransientRelDestReceiver(InvalidOid);
152
153 case DestTupleQueue:
154 return CreateTupleQueueDestReceiver(NULL);
155 }
156
157 /* should never get here */
158 pg_unreachable();
159 }
160
161 /* ----------------
162 * EndCommand - clean up the destination at end of command
163 * ----------------
164 */
165 void
EndCommand(const QueryCompletion * qc,CommandDest dest,bool force_undecorated_output)166 EndCommand(const QueryCompletion *qc, CommandDest dest, bool force_undecorated_output)
167 {
168 char completionTag[COMPLETION_TAG_BUFSIZE];
169 CommandTag tag;
170 const char *tagname;
171
172 switch (dest)
173 {
174 case DestRemote:
175 case DestRemoteExecute:
176 case DestRemoteSimple:
177
178 /*
179 * We assume the tagname is plain ASCII and therefore requires no
180 * encoding conversion.
181 *
182 * We no longer display LastOid, but to preserve the wire
183 * protocol, we write InvalidOid where the LastOid used to be
184 * written.
185 *
186 * All cases where LastOid was written also write nprocessed
187 * count, so just Assert that rather than having an extra test.
188 */
189 tag = qc->commandTag;
190 tagname = GetCommandTagName(tag);
191
192 if (command_tag_display_rowcount(tag) && !force_undecorated_output)
193 snprintf(completionTag, COMPLETION_TAG_BUFSIZE,
194 tag == CMDTAG_INSERT ?
195 "%s 0 " UINT64_FORMAT : "%s " UINT64_FORMAT,
196 tagname, qc->nprocessed);
197 else
198 snprintf(completionTag, COMPLETION_TAG_BUFSIZE, "%s", tagname);
199 pq_putmessage('C', completionTag, strlen(completionTag) + 1);
200
201 case DestNone:
202 case DestDebug:
203 case DestSPI:
204 case DestTuplestore:
205 case DestIntoRel:
206 case DestCopyOut:
207 case DestSQLFunction:
208 case DestTransientRel:
209 case DestTupleQueue:
210 break;
211 }
212 }
213
214 /* ----------------
215 * EndReplicationCommand - stripped down version of EndCommand
216 *
217 * For use by replication commands.
218 * ----------------
219 */
220 void
EndReplicationCommand(const char * commandTag)221 EndReplicationCommand(const char *commandTag)
222 {
223 pq_putmessage('C', commandTag, strlen(commandTag) + 1);
224 }
225
226 /* ----------------
227 * NullCommand - tell dest that an empty query string was recognized
228 *
229 * In FE/BE protocol version 1.0, this hack is necessary to support
230 * libpq's crufty way of determining whether a multiple-command
231 * query string is done. In protocol 2.0 it's probably not really
232 * necessary to distinguish empty queries anymore, but we still do it
233 * for backwards compatibility with 1.0. In protocol 3.0 it has some
234 * use again, since it ensures that there will be a recognizable end
235 * to the response to an Execute message.
236 * ----------------
237 */
238 void
NullCommand(CommandDest dest)239 NullCommand(CommandDest dest)
240 {
241 switch (dest)
242 {
243 case DestRemote:
244 case DestRemoteExecute:
245 case DestRemoteSimple:
246
247 /*
248 * tell the fe that we saw an empty query string. In protocols
249 * before 3.0 this has a useless empty-string message body.
250 */
251 if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 3)
252 pq_putemptymessage('I');
253 else
254 pq_putmessage('I', "", 1);
255 break;
256
257 case DestNone:
258 case DestDebug:
259 case DestSPI:
260 case DestTuplestore:
261 case DestIntoRel:
262 case DestCopyOut:
263 case DestSQLFunction:
264 case DestTransientRel:
265 case DestTupleQueue:
266 break;
267 }
268 }
269
270 /* ----------------
271 * ReadyForQuery - tell dest that we are ready for a new query
272 *
273 * The ReadyForQuery message is sent so that the FE can tell when
274 * we are done processing a query string.
275 * In versions 3.0 and up, it also carries a transaction state indicator.
276 *
277 * Note that by flushing the stdio buffer here, we can avoid doing it
278 * most other places and thus reduce the number of separate packets sent.
279 * ----------------
280 */
281 void
ReadyForQuery(CommandDest dest)282 ReadyForQuery(CommandDest dest)
283 {
284 switch (dest)
285 {
286 case DestRemote:
287 case DestRemoteExecute:
288 case DestRemoteSimple:
289 if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 3)
290 {
291 StringInfoData buf;
292
293 pq_beginmessage(&buf, 'Z');
294 pq_sendbyte(&buf, TransactionBlockStatusCode());
295 pq_endmessage(&buf);
296 }
297 else
298 pq_putemptymessage('Z');
299 /* Flush output at end of cycle in any case. */
300 pq_flush();
301 break;
302
303 case DestNone:
304 case DestDebug:
305 case DestSPI:
306 case DestTuplestore:
307 case DestIntoRel:
308 case DestCopyOut:
309 case DestSQLFunction:
310 case DestTransientRel:
311 case DestTupleQueue:
312 break;
313 }
314 }
315