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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) 1996-2019, 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"
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
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
103 BeginCommand(const char *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 *
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:
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  }
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
166 EndCommand(const char *commandTag, CommandDest dest)
167 {
168  switch (dest)
169  {
170  case DestRemote:
171  case DestRemoteExecute:
172  case DestRemoteSimple:
173 
174  /*
175  * We assume the commandTag is plain ASCII and therefore requires
176  * no encoding conversion.
177  */
178  pq_putmessage('C', commandTag, strlen(commandTag) + 1);
179  break;
180 
181  case DestNone:
182  case DestDebug:
183  case DestSPI:
184  case DestTuplestore:
185  case DestIntoRel:
186  case DestCopyOut:
187  case DestSQLFunction:
188  case DestTransientRel:
189  case DestTupleQueue:
190  break;
191  }
192 }
193 
194 /* ----------------
195  * NullCommand - tell dest that an empty query string was recognized
196  *
197  * In FE/BE protocol version 1.0, this hack is necessary to support
198  * libpq's crufty way of determining whether a multiple-command
199  * query string is done. In protocol 2.0 it's probably not really
200  * necessary to distinguish empty queries anymore, but we still do it
201  * for backwards compatibility with 1.0. In protocol 3.0 it has some
202  * use again, since it ensures that there will be a recognizable end
203  * to the response to an Execute message.
204  * ----------------
205  */
206 void
208 {
209  switch (dest)
210  {
211  case DestRemote:
212  case DestRemoteExecute:
213  case DestRemoteSimple:
214 
215  /*
216  * tell the fe that we saw an empty query string. In protocols
217  * before 3.0 this has a useless empty-string message body.
218  */
220  pq_putemptymessage('I');
221  else
222  pq_putmessage('I', "", 1);
223  break;
224 
225  case DestNone:
226  case DestDebug:
227  case DestSPI:
228  case DestTuplestore:
229  case DestIntoRel:
230  case DestCopyOut:
231  case DestSQLFunction:
232  case DestTransientRel:
233  case DestTupleQueue:
234  break;
235  }
236 }
237 
238 /* ----------------
239  * ReadyForQuery - tell dest that we are ready for a new query
240  *
241  * The ReadyForQuery message is sent so that the FE can tell when
242  * we are done processing a query string.
243  * In versions 3.0 and up, it also carries a transaction state indicator.
244  *
245  * Note that by flushing the stdio buffer here, we can avoid doing it
246  * most other places and thus reduce the number of separate packets sent.
247  * ----------------
248  */
249 void
251 {
252  switch (dest)
253  {
254  case DestRemote:
255  case DestRemoteExecute:
256  case DestRemoteSimple:
258  {
260 
261  pq_beginmessage(&buf, 'Z');
263  pq_endmessage(&buf);
264  }
265  else
266  pq_putemptymessage('Z');
267  /* Flush output at end of cycle in any case. */
268  pq_flush();
269  break;
270 
271  case DestNone:
272  case DestDebug:
273  case DestSPI:
274  case DestTuplestore:
275  case DestIntoRel:
276  case DestCopyOut:
277  case DestSQLFunction:
278  case DestTransientRel:
279  case DestTupleQueue:
280  break;
281  }
282 }
#define pg_unreachable()
Definition: c.h:193
#define pq_flush()
Definition: libpq.h:39
CommandDest
Definition: dest.h:86
static const DestReceiver debugtupDR
Definition: dest.c:75
Definition: dest.h:93
void pq_putemptymessage(char msgtype)
Definition: pqformat.c:390
void BeginCommand(const char *commandTag, CommandDest dest)
Definition: dest.c:103
#define PG_PROTOCOL_MAJOR(v)
Definition: pqcomm.h:104
DestReceiver * None_Receiver
Definition: dest.c:96
char TransactionBlockStatusCode(void)
Definition: xact.c:4667
bool printsimple(TupleTableSlot *slot, DestReceiver *self)
Definition: printsimple.c:58
void pq_beginmessage(StringInfo buf, char msgtype)
Definition: pqformat.c:87
static void pq_sendbyte(StringInfo buf, uint8 byt)
Definition: pqformat.h:161
static bool donothingReceive(TupleTableSlot *slot, DestReceiver *self)
Definition: dest.c:50
void EndCommand(const char *commandTag, CommandDest dest)
Definition: dest.c:166
static const DestReceiver printsimpleDR
Definition: dest.c:80
Definition: dest.h:88
static char * buf
Definition: pg_test_fsync.c:67
DestReceiver * printtup_create_DR(CommandDest dest)
Definition: printtup.c:78
DestReceiver * CreateDestReceiver(CommandDest dest)
Definition: dest.c:113
Definition: dest.h:89
void spi_dest_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
Definition: spi.c:1841
DestReceiver * CreateIntoRelDestReceiver(IntoClause *intoClause)
Definition: createas.c:412
void printsimple_startup(DestReceiver *self, int operation, TupleDesc tupdesc)
Definition: printsimple.c:30
DestReceiver * CreateSQLFunctionDestReceiver(void)
Definition: functions.c:1955
#define unconstify(underlying_type, expr)
Definition: c.h:1194
#define InvalidOid
Definition: postgres_ext.h:36
static void donothingStartup(DestReceiver *self, int operation, TupleDesc typeinfo)
Definition: dest.c:56
bool debugtup(TupleTableSlot *slot, DestReceiver *self)
Definition: printtup.c:614
static const DestReceiver spi_printtupDR
Definition: dest.c:85
DestReceiver * CreateTuplestoreDestReceiver(void)
DestReceiver * CreateTransientRelDestReceiver(Oid transientoid)
Definition: matview.c:430
void ReadyForQuery(CommandDest dest)
Definition: dest.c:250
void pq_endmessage(StringInfo buf)
Definition: pqformat.c:298
DestReceiver * CreateCopyDestReceiver(void)
Definition: copy.c:5199
static const DestReceiver donothingDR
Definition: dest.c:70
#define pq_putmessage(msgtype, s, len)
Definition: libpq.h:42
DestReceiver * CreateTupleQueueDestReceiver(shm_mq_handle *handle)
Definition: tqueue.c:119
void debugStartup(DestReceiver *self, int operation, TupleDesc typeinfo)
Definition: printtup.c:596
ProtocolVersion FrontendProtocol
Definition: globals.c:28
static void donothingCleanup(DestReceiver *self)
Definition: dest.c:61
bool spi_printtup(TupleTableSlot *slot, DestReceiver *self)
Definition: spi.c:1889
void NullCommand(CommandDest dest)
Definition: dest.c:207