Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * parallel_slot.c
4 : * Parallel support for front-end parallel database connections
5 : *
6 : *
7 : * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
8 : * Portions Copyright (c) 1994, Regents of the University of California
9 : *
10 : * src/fe_utils/parallel_slot.c
11 : *
12 : *-------------------------------------------------------------------------
13 : */
14 :
15 : #if defined(WIN32) && FD_SETSIZE < 1024
16 : #error FD_SETSIZE needs to have been increased
17 : #endif
18 :
19 : #include "postgres_fe.h"
20 :
21 : #include <sys/select.h>
22 :
23 : #include "common/logging.h"
24 : #include "fe_utils/cancel.h"
25 : #include "fe_utils/parallel_slot.h"
26 : #include "fe_utils/query_utils.h"
27 :
28 : #define ERRCODE_UNDEFINED_TABLE "42P01"
29 :
30 : static int select_loop(int maxFd, fd_set *workerset);
31 : static bool processQueryResult(ParallelSlot *slot, PGresult *result);
32 :
33 : /*
34 : * Process (and delete) a query result. Returns true if there's no problem,
35 : * false otherwise. It's up to the handler to decide what constitutes a
36 : * problem.
37 : */
38 : static bool
39 16866 : processQueryResult(ParallelSlot *slot, PGresult *result)
40 : {
41 : Assert(slot->handler != NULL);
42 :
43 : /* On failure, the handler should return NULL after freeing the result */
44 16866 : if (!slot->handler(result, slot->connection, slot->handler_context))
45 14 : return false;
46 :
47 : /* Ok, we have to free it ourself */
48 16852 : PQclear(result);
49 16852 : return true;
50 : }
51 :
52 : /*
53 : * Consume all the results generated for the given connection until
54 : * nothing remains. If at least one error is encountered, return false.
55 : * Note that this will block if the connection is busy.
56 : */
57 : static bool
58 288 : consumeQueryResult(ParallelSlot *slot)
59 : {
60 288 : bool ok = true;
61 : PGresult *result;
62 :
63 288 : SetCancelConn(slot->connection);
64 576 : while ((result = PQgetResult(slot->connection)) != NULL)
65 : {
66 288 : if (!processQueryResult(slot, result))
67 14 : ok = false;
68 : }
69 288 : ResetCancelConn();
70 288 : return ok;
71 : }
72 :
73 : /*
74 : * Wait until a file descriptor from the given set becomes readable.
75 : *
76 : * Returns the number of ready descriptors, or -1 on failure (including
77 : * getting a cancel request).
78 : */
79 : static int
80 16670 : select_loop(int maxFd, fd_set *workerset)
81 : {
82 : int i;
83 16670 : fd_set saveSet = *workerset;
84 :
85 16670 : if (CancelRequested)
86 0 : return -1;
87 :
88 : for (;;)
89 0 : {
90 : /*
91 : * On Windows, we need to check once in a while for cancel requests;
92 : * on other platforms we rely on select() returning when interrupted.
93 : */
94 : struct timeval *tvp;
95 : #ifdef WIN32
96 : struct timeval tv = {0, 1000000};
97 :
98 : tvp = &tv;
99 : #else
100 16670 : tvp = NULL;
101 : #endif
102 :
103 16670 : *workerset = saveSet;
104 16670 : i = select(maxFd + 1, workerset, NULL, NULL, tvp);
105 :
106 : #ifdef WIN32
107 : if (i == SOCKET_ERROR)
108 : {
109 : i = -1;
110 :
111 : if (WSAGetLastError() == WSAEINTR)
112 : errno = EINTR;
113 : }
114 : #endif
115 :
116 16670 : if (i < 0 && errno == EINTR)
117 0 : continue; /* ignore this */
118 16670 : if (i < 0 || CancelRequested)
119 0 : return -1; /* but not this */
120 16670 : if (i == 0)
121 0 : continue; /* timeout (Win32 only) */
122 16670 : break;
123 : }
124 :
125 16670 : return i;
126 : }
127 :
128 : /*
129 : * Return the offset of a suitable idle slot, or -1 if none are available. If
130 : * the given dbname is not null, only idle slots connected to the given
131 : * database are considered suitable, otherwise all idle connected slots are
132 : * considered suitable.
133 : */
134 : static int
135 33534 : find_matching_idle_slot(const ParallelSlotArray *sa, const char *dbname)
136 : {
137 : int i;
138 :
139 50462 : for (i = 0; i < sa->numslots; i++)
140 : {
141 33758 : if (sa->slots[i].inUse)
142 16894 : continue;
143 :
144 16864 : if (sa->slots[i].connection == NULL)
145 12 : continue;
146 :
147 16852 : if (dbname == NULL ||
148 11650 : strcmp(PQdb(sa->slots[i].connection), dbname) == 0)
149 16830 : return i;
150 : }
151 16704 : return -1;
152 : }
153 :
154 : /*
155 : * Return the offset of the first slot without a database connection, or -1 if
156 : * all slots are connected.
157 : */
158 : static int
159 16908 : find_unconnected_slot(const ParallelSlotArray *sa)
160 : {
161 : int i;
162 :
163 33750 : for (i = 0; i < sa->numslots; i++)
164 : {
165 17058 : if (sa->slots[i].inUse)
166 16820 : continue;
167 :
168 238 : if (sa->slots[i].connection == NULL)
169 216 : return i;
170 : }
171 :
172 16692 : return -1;
173 : }
174 :
175 : /*
176 : * Return the offset of the first idle slot, or -1 if all slots are busy.
177 : */
178 : static int
179 16692 : find_any_idle_slot(const ParallelSlotArray *sa)
180 : {
181 : int i;
182 :
183 33506 : for (i = 0; i < sa->numslots; i++)
184 16836 : if (!sa->slots[i].inUse)
185 22 : return i;
186 :
187 16670 : return -1;
188 : }
189 :
190 : /*
191 : * Wait for any slot's connection to have query results, consume the results,
192 : * and update the slot's status as appropriate. Returns true on success,
193 : * false on cancellation, on error, or if no slots are connected.
194 : */
195 : static bool
196 16670 : wait_on_slots(ParallelSlotArray *sa)
197 : {
198 : int i;
199 : fd_set slotset;
200 16670 : int maxFd = 0;
201 16670 : PGconn *cancelconn = NULL;
202 :
203 : /* We must reconstruct the fd_set for each call to select_loop */
204 16670 : FD_ZERO(&slotset);
205 :
206 33484 : for (i = 0; i < sa->numslots; i++)
207 : {
208 : int sock;
209 :
210 : /* We shouldn't get here if we still have slots without connections */
211 : Assert(sa->slots[i].connection != NULL);
212 :
213 16814 : sock = PQsocket(sa->slots[i].connection);
214 :
215 : /*
216 : * We don't really expect any connections to lose their sockets after
217 : * startup, but just in case, cope by ignoring them.
218 : */
219 16814 : if (sock < 0)
220 0 : continue;
221 :
222 : /* Keep track of the first valid connection we see. */
223 16814 : if (cancelconn == NULL)
224 16670 : cancelconn = sa->slots[i].connection;
225 :
226 16814 : FD_SET(sock, &slotset);
227 16814 : if (sock > maxFd)
228 16814 : maxFd = sock;
229 : }
230 :
231 : /*
232 : * If we get this far with no valid connections, processing cannot
233 : * continue.
234 : */
235 16670 : if (cancelconn == NULL)
236 0 : return false;
237 :
238 16670 : SetCancelConn(cancelconn);
239 16670 : i = select_loop(maxFd, &slotset);
240 16670 : ResetCancelConn();
241 :
242 : /* failure? */
243 16670 : if (i < 0)
244 0 : return false;
245 :
246 33484 : for (i = 0; i < sa->numslots; i++)
247 : {
248 : int sock;
249 :
250 16814 : sock = PQsocket(sa->slots[i].connection);
251 :
252 16814 : if (sock >= 0 && FD_ISSET(sock, &slotset))
253 : {
254 : /* select() says input is available, so consume it */
255 16670 : PQconsumeInput(sa->slots[i].connection);
256 : }
257 :
258 : /* Collect result(s) as long as any are available */
259 33392 : while (!PQisBusy(sa->slots[i].connection))
260 : {
261 33156 : PGresult *result = PQgetResult(sa->slots[i].connection);
262 :
263 33156 : if (result != NULL)
264 : {
265 : /* Handle and discard the command result */
266 16578 : if (!processQueryResult(&sa->slots[i], result))
267 0 : return false;
268 : }
269 : else
270 : {
271 : /* This connection has become idle */
272 16578 : sa->slots[i].inUse = false;
273 16578 : ParallelSlotClearHandler(&sa->slots[i]);
274 16578 : break;
275 : }
276 : }
277 : }
278 16670 : return true;
279 : }
280 :
281 : /*
282 : * Open a new database connection using the stored connection parameters and
283 : * optionally a given dbname if not null, execute the stored initial command if
284 : * any, and associate the new connection with the given slot.
285 : */
286 : static void
287 34 : connect_slot(ParallelSlotArray *sa, int slotno, const char *dbname)
288 : {
289 : const char *old_override;
290 34 : ParallelSlot *slot = &sa->slots[slotno];
291 :
292 34 : old_override = sa->cparams->override_dbname;
293 34 : if (dbname)
294 28 : sa->cparams->override_dbname = dbname;
295 34 : slot->connection = connectDatabase(sa->cparams, sa->progname, sa->echo, false, true);
296 34 : sa->cparams->override_dbname = old_override;
297 :
298 34 : if (PQsocket(slot->connection) >= FD_SETSIZE)
299 0 : pg_fatal("too many jobs for this platform");
300 :
301 : /* Setup the connection using the supplied command, if any. */
302 34 : if (sa->initcmd)
303 0 : executeCommand(slot->connection, sa->initcmd, sa->echo);
304 34 : }
305 :
306 : /*
307 : * ParallelSlotsGetIdle
308 : * Return a connection slot that is ready to execute a command.
309 : *
310 : * The slot returned is chosen as follows:
311 : *
312 : * If any idle slot already has an open connection, and if either dbname is
313 : * null or the existing connection is to the given database, that slot will be
314 : * returned allowing the connection to be reused.
315 : *
316 : * Otherwise, if any idle slot is not yet connected to any database, the slot
317 : * will be returned with it's connection opened using the stored cparams and
318 : * optionally the given dbname if not null.
319 : *
320 : * Otherwise, if any idle slot exists, an idle slot will be chosen and returned
321 : * after having it's connection disconnected and reconnected using the stored
322 : * cparams and optionally the given dbname if not null.
323 : *
324 : * Otherwise, if any slots have connections that are busy, we loop on select()
325 : * until one socket becomes available. When this happens, we read the whole
326 : * set and mark as free all sockets that become available. We then select a
327 : * slot using the same rules as above.
328 : *
329 : * Otherwise, we cannot return a slot, which is an error, and NULL is returned.
330 : *
331 : * For any connection created, if the stored initcmd is not null, it will be
332 : * executed as a command on the newly formed connection before the slot is
333 : * returned.
334 : *
335 : * If an error occurs, NULL is returned.
336 : */
337 : ParallelSlot *
338 33534 : ParallelSlotsGetIdle(ParallelSlotArray *sa, const char *dbname)
339 : {
340 : int offset;
341 :
342 : Assert(sa);
343 : Assert(sa->numslots > 0);
344 :
345 : while (1)
346 : {
347 : /* First choice: a slot already connected to the desired database. */
348 33534 : offset = find_matching_idle_slot(sa, dbname);
349 33534 : if (offset >= 0)
350 : {
351 16830 : sa->slots[offset].inUse = true;
352 16830 : return &sa->slots[offset];
353 : }
354 :
355 : /* Second choice: a slot not connected to any database. */
356 16704 : offset = find_unconnected_slot(sa);
357 16704 : if (offset >= 0)
358 : {
359 12 : connect_slot(sa, offset, dbname);
360 12 : sa->slots[offset].inUse = true;
361 12 : return &sa->slots[offset];
362 : }
363 :
364 : /* Third choice: a slot connected to the wrong database. */
365 16692 : offset = find_any_idle_slot(sa);
366 16692 : if (offset >= 0)
367 : {
368 22 : disconnectDatabase(sa->slots[offset].connection);
369 22 : sa->slots[offset].connection = NULL;
370 22 : connect_slot(sa, offset, dbname);
371 22 : sa->slots[offset].inUse = true;
372 22 : return &sa->slots[offset];
373 : }
374 :
375 : /*
376 : * Fourth choice: block until one or more slots become available. If
377 : * any slots hit a fatal error, we'll find out about that here and
378 : * return NULL.
379 : */
380 16670 : if (!wait_on_slots(sa))
381 0 : return NULL;
382 : }
383 : }
384 :
385 : /*
386 : * ParallelSlotsSetup
387 : * Prepare a set of parallel slots but do not connect to any database.
388 : *
389 : * This creates and initializes a set of slots, marking all parallel slots as
390 : * free and ready to use. Establishing connections is delayed until requesting
391 : * a free slot. The cparams, progname, echo, and initcmd are stored for later
392 : * use and must remain valid for the lifetime of the returned array.
393 : */
394 : ParallelSlotArray *
395 210 : ParallelSlotsSetup(int numslots, ConnParams *cparams, const char *progname,
396 : bool echo, const char *initcmd)
397 : {
398 : ParallelSlotArray *sa;
399 :
400 : Assert(numslots > 0);
401 : Assert(cparams != NULL);
402 : Assert(progname != NULL);
403 :
404 210 : sa = (ParallelSlotArray *) palloc0(offsetof(ParallelSlotArray, slots) +
405 210 : numslots * sizeof(ParallelSlot));
406 :
407 210 : sa->numslots = numslots;
408 210 : sa->cparams = cparams;
409 210 : sa->progname = progname;
410 210 : sa->echo = echo;
411 210 : sa->initcmd = initcmd;
412 :
413 210 : return sa;
414 : }
415 :
416 : /*
417 : * ParallelSlotsAdoptConn
418 : * Assign an open connection to the slots array for reuse.
419 : *
420 : * This turns over ownership of an open connection to a slots array. The
421 : * caller should not further use or close the connection. All the connection's
422 : * parameters (user, host, port, etc.) except possibly dbname should match
423 : * those of the slots array's cparams, as given in ParallelSlotsSetup. If
424 : * these parameters differ, subsequent behavior is undefined.
425 : */
426 : void
427 204 : ParallelSlotsAdoptConn(ParallelSlotArray *sa, PGconn *conn)
428 : {
429 : int offset;
430 :
431 204 : offset = find_unconnected_slot(sa);
432 204 : if (offset >= 0)
433 204 : sa->slots[offset].connection = conn;
434 : else
435 0 : disconnectDatabase(conn);
436 204 : }
437 :
438 : /*
439 : * ParallelSlotsTerminate
440 : * Clean up a set of parallel slots
441 : *
442 : * Iterate through all connections in a given set of ParallelSlots and
443 : * terminate all connections.
444 : */
445 : void
446 210 : ParallelSlotsTerminate(ParallelSlotArray *sa)
447 : {
448 : int i;
449 :
450 426 : for (i = 0; i < sa->numslots; i++)
451 : {
452 216 : PGconn *conn = sa->slots[i].connection;
453 :
454 216 : if (conn == NULL)
455 0 : continue;
456 :
457 216 : disconnectDatabase(conn);
458 : }
459 210 : }
460 :
461 : /*
462 : * ParallelSlotsWaitCompletion
463 : *
464 : * Wait for all connections to finish, returning false if at least one
465 : * error has been found on the way.
466 : */
467 : bool
468 280 : ParallelSlotsWaitCompletion(ParallelSlotArray *sa)
469 : {
470 : int i;
471 :
472 554 : for (i = 0; i < sa->numslots; i++)
473 : {
474 288 : if (sa->slots[i].connection == NULL)
475 0 : continue;
476 288 : if (!consumeQueryResult(&sa->slots[i]))
477 14 : return false;
478 : /* Mark connection as idle */
479 274 : sa->slots[i].inUse = false;
480 274 : ParallelSlotClearHandler(&sa->slots[i]);
481 : }
482 :
483 266 : return true;
484 : }
485 :
486 : /*
487 : * TableCommandResultHandler
488 : *
489 : * ParallelSlotResultHandler for results of commands (not queries) against
490 : * tables.
491 : *
492 : * Requires that the result status is either PGRES_COMMAND_OK or an error about
493 : * a missing table. This is useful for utilities that compile a list of tables
494 : * to process and then run commands (vacuum, reindex, or whatever) against
495 : * those tables, as there is a race condition between the time the list is
496 : * compiled and the time the command attempts to open the table.
497 : *
498 : * For missing tables, logs an error but allows processing to continue.
499 : *
500 : * For all other errors, logs an error and terminates further processing.
501 : *
502 : * res: PGresult from the query executed on the slot's connection
503 : * conn: connection belonging to the slot
504 : * context: unused
505 : */
506 : bool
507 5210 : TableCommandResultHandler(PGresult *res, PGconn *conn, void *context)
508 : {
509 : Assert(res != NULL);
510 : Assert(conn != NULL);
511 :
512 : /*
513 : * If it's an error, report it. Errors about a missing table are harmless
514 : * so we continue processing; but die for other errors.
515 : */
516 5210 : if (PQresultStatus(res) != PGRES_COMMAND_OK)
517 : {
518 14 : char *sqlState = PQresultErrorField(res, PG_DIAG_SQLSTATE);
519 :
520 14 : pg_log_error("processing of database \"%s\" failed: %s",
521 : PQdb(conn), PQerrorMessage(conn));
522 :
523 14 : if (sqlState && strcmp(sqlState, ERRCODE_UNDEFINED_TABLE) != 0)
524 : {
525 14 : PQclear(res);
526 14 : return false;
527 : }
528 : }
529 :
530 5196 : return true;
531 : }
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