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1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * parallel.c
4 : : * Infrastructure for launching parallel workers
5 : : *
6 : : * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
7 : : * Portions Copyright (c) 1994, Regents of the University of California
8 : : *
9 : : * IDENTIFICATION
10 : : * src/backend/access/transam/parallel.c
11 : : *
12 : : *-------------------------------------------------------------------------
13 : : */
14 : :
15 : : #include "postgres.h"
16 : :
17 : : #include "access/brin.h"
18 : : #include "access/gin.h"
19 : : #include "access/nbtree.h"
20 : : #include "access/parallel.h"
21 : : #include "access/session.h"
22 : : #include "access/xact.h"
23 : : #include "access/xlog.h"
24 : : #include "catalog/index.h"
25 : : #include "catalog/namespace.h"
26 : : #include "catalog/pg_enum.h"
27 : : #include "catalog/storage.h"
28 : : #include "commands/async.h"
29 : : #include "commands/vacuum.h"
30 : : #include "executor/execParallel.h"
31 : : #include "libpq/libpq.h"
32 : : #include "libpq/pqformat.h"
33 : : #include "libpq/pqmq.h"
34 : : #include "miscadmin.h"
35 : : #include "optimizer/optimizer.h"
36 : : #include "pgstat.h"
37 : : #include "storage/ipc.h"
38 : : #include "storage/predicate.h"
39 : : #include "storage/spin.h"
40 : : #include "tcop/tcopprot.h"
41 : : #include "utils/combocid.h"
42 : : #include "utils/guc.h"
43 : : #include "utils/inval.h"
44 : : #include "utils/memutils.h"
45 : : #include "utils/relmapper.h"
46 : : #include "utils/snapmgr.h"
47 : :
48 : : /*
49 : : * We don't want to waste a lot of memory on an error queue which, most of
50 : : * the time, will process only a handful of small messages. However, it is
51 : : * desirable to make it large enough that a typical ErrorResponse can be sent
52 : : * without blocking. That way, a worker that errors out can write the whole
53 : : * message into the queue and terminate without waiting for the user backend.
54 : : */
55 : : #define PARALLEL_ERROR_QUEUE_SIZE 16384
56 : :
57 : : /* Magic number for parallel context TOC. */
58 : : #define PARALLEL_MAGIC 0x50477c7c
59 : :
60 : : /*
61 : : * Magic numbers for per-context parallel state sharing. Higher-level code
62 : : * should use smaller values, leaving these very large ones for use by this
63 : : * module.
64 : : */
65 : : #define PARALLEL_KEY_FIXED UINT64CONST(0xFFFFFFFFFFFF0001)
66 : : #define PARALLEL_KEY_ERROR_QUEUE UINT64CONST(0xFFFFFFFFFFFF0002)
67 : : #define PARALLEL_KEY_LIBRARY UINT64CONST(0xFFFFFFFFFFFF0003)
68 : : #define PARALLEL_KEY_GUC UINT64CONST(0xFFFFFFFFFFFF0004)
69 : : #define PARALLEL_KEY_COMBO_CID UINT64CONST(0xFFFFFFFFFFFF0005)
70 : : #define PARALLEL_KEY_TRANSACTION_SNAPSHOT UINT64CONST(0xFFFFFFFFFFFF0006)
71 : : #define PARALLEL_KEY_ACTIVE_SNAPSHOT UINT64CONST(0xFFFFFFFFFFFF0007)
72 : : #define PARALLEL_KEY_TRANSACTION_STATE UINT64CONST(0xFFFFFFFFFFFF0008)
73 : : #define PARALLEL_KEY_ENTRYPOINT UINT64CONST(0xFFFFFFFFFFFF0009)
74 : : #define PARALLEL_KEY_SESSION_DSM UINT64CONST(0xFFFFFFFFFFFF000A)
75 : : #define PARALLEL_KEY_PENDING_SYNCS UINT64CONST(0xFFFFFFFFFFFF000B)
76 : : #define PARALLEL_KEY_REINDEX_STATE UINT64CONST(0xFFFFFFFFFFFF000C)
77 : : #define PARALLEL_KEY_RELMAPPER_STATE UINT64CONST(0xFFFFFFFFFFFF000D)
78 : : #define PARALLEL_KEY_UNCOMMITTEDENUMS UINT64CONST(0xFFFFFFFFFFFF000E)
79 : : #define PARALLEL_KEY_CLIENTCONNINFO UINT64CONST(0xFFFFFFFFFFFF000F)
80 : :
81 : : /* Fixed-size parallel state. */
82 : : typedef struct FixedParallelState
83 : : {
84 : : /* Fixed-size state that workers must restore. */
85 : : Oid database_id;
86 : : Oid authenticated_user_id;
87 : : Oid session_user_id;
88 : : Oid outer_user_id;
89 : : Oid current_user_id;
90 : : Oid temp_namespace_id;
91 : : Oid temp_toast_namespace_id;
92 : : int sec_context;
93 : : bool session_user_is_superuser;
94 : : bool role_is_superuser;
95 : : PGPROC *parallel_leader_pgproc;
96 : : pid_t parallel_leader_pid;
97 : : ProcNumber parallel_leader_proc_number;
98 : : TimestampTz xact_ts;
99 : : TimestampTz stmt_ts;
100 : : SerializableXactHandle serializable_xact_handle;
101 : :
102 : : /* Mutex protects remaining fields. */
103 : : slock_t mutex;
104 : :
105 : : /* Maximum XactLastRecEnd of any worker. */
106 : : XLogRecPtr last_xlog_end;
107 : : } FixedParallelState;
108 : :
109 : : /*
110 : : * Our parallel worker number. We initialize this to -1, meaning that we are
111 : : * not a parallel worker. In parallel workers, it will be set to a value >= 0
112 : : * and < the number of workers before any user code is invoked; each parallel
113 : : * worker will get a different parallel worker number.
114 : : */
115 : : int ParallelWorkerNumber = -1;
116 : :
117 : : /* Is there a parallel message pending which we need to receive? */
118 : : volatile sig_atomic_t ParallelMessagePending = false;
119 : :
120 : : /* Are we initializing a parallel worker? */
121 : : bool InitializingParallelWorker = false;
122 : :
123 : : /* Pointer to our fixed parallel state. */
124 : : static FixedParallelState *MyFixedParallelState;
125 : :
126 : : /* List of active parallel contexts. */
127 : : static dlist_head pcxt_list = DLIST_STATIC_INIT(pcxt_list);
128 : :
129 : : /* Backend-local copy of data from FixedParallelState. */
130 : : static pid_t ParallelLeaderPid;
131 : :
132 : : /*
133 : : * List of internal parallel worker entry points. We need this for
134 : : * reasons explained in LookupParallelWorkerFunction(), below.
135 : : */
136 : : static const struct
137 : : {
138 : : const char *fn_name;
139 : : parallel_worker_main_type fn_addr;
140 : : } InternalParallelWorkers[] =
141 : :
142 : : {
143 : : {
144 : : "ParallelQueryMain", ParallelQueryMain
145 : : },
146 : : {
147 : : "_bt_parallel_build_main", _bt_parallel_build_main
148 : : },
149 : : {
150 : : "_brin_parallel_build_main", _brin_parallel_build_main
151 : : },
152 : : {
153 : : "_gin_parallel_build_main", _gin_parallel_build_main
154 : : },
155 : : {
156 : : "parallel_vacuum_main", parallel_vacuum_main
157 : : }
158 : : };
159 : :
160 : : /* Private functions. */
161 : : static void ProcessParallelMessage(ParallelContext *pcxt, int i, StringInfo msg);
162 : : static void WaitForParallelWorkersToExit(ParallelContext *pcxt);
163 : : static parallel_worker_main_type LookupParallelWorkerFunction(const char *libraryname, const char *funcname);
164 : : static void ParallelWorkerShutdown(int code, Datum arg);
165 : :
166 : :
167 : : /*
168 : : * Establish a new parallel context. This should be done after entering
169 : : * parallel mode, and (unless there is an error) the context should be
170 : : * destroyed before exiting the current subtransaction.
171 : : */
172 : : ParallelContext *
173 : 155 : CreateParallelContext(const char *library_name, const char *function_name,
174 : : int nworkers)
175 : : {
176 : 155 : MemoryContext oldcontext;
177 : 155 : ParallelContext *pcxt;
178 : :
179 : : /* It is unsafe to create a parallel context if not in parallel mode. */
180 [ + - ]: 155 : Assert(IsInParallelMode());
181 : :
182 : : /* Number of workers should be non-negative. */
183 [ + - ]: 155 : Assert(nworkers >= 0);
184 : :
185 : : /* We might be running in a short-lived memory context. */
186 : 155 : oldcontext = MemoryContextSwitchTo(TopTransactionContext);
187 : :
188 : : /* Initialize a new ParallelContext. */
189 : 155 : pcxt = palloc0_object(ParallelContext);
190 : 155 : pcxt->subid = GetCurrentSubTransactionId();
191 : 155 : pcxt->nworkers = nworkers;
192 : 155 : pcxt->nworkers_to_launch = nworkers;
193 : 155 : pcxt->library_name = pstrdup(library_name);
194 : 155 : pcxt->function_name = pstrdup(function_name);
195 : 155 : pcxt->error_context_stack = error_context_stack;
196 : 155 : shm_toc_initialize_estimator(&pcxt->estimator);
197 : 155 : dlist_push_head(&pcxt_list, &pcxt->node);
198 : :
199 : : /* Restore previous memory context. */
200 : 155 : MemoryContextSwitchTo(oldcontext);
201 : :
202 : 310 : return pcxt;
203 : 155 : }
204 : :
205 : : /*
206 : : * Establish the dynamic shared memory segment for a parallel context and
207 : : * copy state and other bookkeeping information that will be needed by
208 : : * parallel workers into it.
209 : : */
210 : : void
211 : 155 : InitializeParallelDSM(ParallelContext *pcxt)
212 : : {
213 : 155 : MemoryContext oldcontext;
214 : 155 : Size library_len = 0;
215 : 155 : Size guc_len = 0;
216 : 155 : Size combocidlen = 0;
217 : 155 : Size tsnaplen = 0;
218 : 155 : Size asnaplen = 0;
219 : 155 : Size tstatelen = 0;
220 : 155 : Size pendingsyncslen = 0;
221 : 155 : Size reindexlen = 0;
222 : 155 : Size relmapperlen = 0;
223 : 155 : Size uncommittedenumslen = 0;
224 : 155 : Size clientconninfolen = 0;
225 : 155 : Size segsize = 0;
226 : 155 : int i;
227 : 155 : FixedParallelState *fps;
228 : 155 : dsm_handle session_dsm_handle = DSM_HANDLE_INVALID;
229 : 155 : Snapshot transaction_snapshot = GetTransactionSnapshot();
230 : 155 : Snapshot active_snapshot = GetActiveSnapshot();
231 : :
232 : : /* We might be running in a very short-lived memory context. */
233 : 155 : oldcontext = MemoryContextSwitchTo(TopTransactionContext);
234 : :
235 : : /* Allow space to store the fixed-size parallel state. */
236 : 155 : shm_toc_estimate_chunk(&pcxt->estimator, sizeof(FixedParallelState));
237 : 155 : shm_toc_estimate_keys(&pcxt->estimator, 1);
238 : :
239 : : /*
240 : : * If we manage to reach here while non-interruptible, it's unsafe to
241 : : * launch any workers: we would fail to process interrupts sent by them.
242 : : * We can deal with that edge case by pretending no workers were
243 : : * requested.
244 : : */
245 [ + - + - : 155 : if (!INTERRUPTS_CAN_BE_PROCESSED())
- + ]
246 : 0 : pcxt->nworkers = 0;
247 : :
248 : : /*
249 : : * Normally, the user will have requested at least one worker process, but
250 : : * if by chance they have not, we can skip a bunch of things here.
251 : : */
252 [ + - ]: 155 : if (pcxt->nworkers > 0)
253 : : {
254 : : /* Get (or create) the per-session DSM segment's handle. */
255 : 155 : session_dsm_handle = GetSessionDsmHandle();
256 : :
257 : : /*
258 : : * If we weren't able to create a per-session DSM segment, then we can
259 : : * continue but we can't safely launch any workers because their
260 : : * record typmods would be incompatible so they couldn't exchange
261 : : * tuples.
262 : : */
263 [ + - ]: 155 : if (session_dsm_handle == DSM_HANDLE_INVALID)
264 : 0 : pcxt->nworkers = 0;
265 : 155 : }
266 : :
267 [ + - ]: 155 : if (pcxt->nworkers > 0)
268 : : {
269 : : StaticAssertDecl(BUFFERALIGN(PARALLEL_ERROR_QUEUE_SIZE) ==
270 : : PARALLEL_ERROR_QUEUE_SIZE,
271 : : "parallel error queue size not buffer-aligned");
272 : :
273 : : /* Estimate space for various kinds of state sharing. */
274 : 155 : library_len = EstimateLibraryStateSpace();
275 : 155 : shm_toc_estimate_chunk(&pcxt->estimator, library_len);
276 : 155 : guc_len = EstimateGUCStateSpace();
277 : 155 : shm_toc_estimate_chunk(&pcxt->estimator, guc_len);
278 : 155 : combocidlen = EstimateComboCIDStateSpace();
279 : 155 : shm_toc_estimate_chunk(&pcxt->estimator, combocidlen);
280 [ + - ]: 155 : if (IsolationUsesXactSnapshot())
281 : : {
282 : 0 : tsnaplen = EstimateSnapshotSpace(transaction_snapshot);
283 : 0 : shm_toc_estimate_chunk(&pcxt->estimator, tsnaplen);
284 : 0 : }
285 : 155 : asnaplen = EstimateSnapshotSpace(active_snapshot);
286 : 155 : shm_toc_estimate_chunk(&pcxt->estimator, asnaplen);
287 : 155 : tstatelen = EstimateTransactionStateSpace();
288 : 155 : shm_toc_estimate_chunk(&pcxt->estimator, tstatelen);
289 : 155 : shm_toc_estimate_chunk(&pcxt->estimator, sizeof(dsm_handle));
290 : 155 : pendingsyncslen = EstimatePendingSyncsSpace();
291 : 155 : shm_toc_estimate_chunk(&pcxt->estimator, pendingsyncslen);
292 : 155 : reindexlen = EstimateReindexStateSpace();
293 : 155 : shm_toc_estimate_chunk(&pcxt->estimator, reindexlen);
294 : 155 : relmapperlen = EstimateRelationMapSpace();
295 : 155 : shm_toc_estimate_chunk(&pcxt->estimator, relmapperlen);
296 : 155 : uncommittedenumslen = EstimateUncommittedEnumsSpace();
297 : 155 : shm_toc_estimate_chunk(&pcxt->estimator, uncommittedenumslen);
298 : 155 : clientconninfolen = EstimateClientConnectionInfoSpace();
299 : 155 : shm_toc_estimate_chunk(&pcxt->estimator, clientconninfolen);
300 : : /* If you add more chunks here, you probably need to add keys. */
301 : 155 : shm_toc_estimate_keys(&pcxt->estimator, 12);
302 : :
303 : : /* Estimate space need for error queues. */
304 : 155 : shm_toc_estimate_chunk(&pcxt->estimator,
305 : : mul_size(PARALLEL_ERROR_QUEUE_SIZE,
306 : : pcxt->nworkers));
307 : 155 : shm_toc_estimate_keys(&pcxt->estimator, 1);
308 : :
309 : : /* Estimate how much we'll need for the entrypoint info. */
310 : 155 : shm_toc_estimate_chunk(&pcxt->estimator, strlen(pcxt->library_name) +
311 : : strlen(pcxt->function_name) + 2);
312 : 155 : shm_toc_estimate_keys(&pcxt->estimator, 1);
313 : 155 : }
314 : :
315 : : /*
316 : : * Create DSM and initialize with new table of contents. But if the user
317 : : * didn't request any workers, then don't bother creating a dynamic shared
318 : : * memory segment; instead, just use backend-private memory.
319 : : *
320 : : * Also, if we can't create a dynamic shared memory segment because the
321 : : * maximum number of segments have already been created, then fall back to
322 : : * backend-private memory, and plan not to use any workers. We hope this
323 : : * won't happen very often, but it's better to abandon the use of
324 : : * parallelism than to fail outright.
325 : : */
326 : 155 : segsize = shm_toc_estimate(&pcxt->estimator);
327 [ + - ]: 155 : if (pcxt->nworkers > 0)
328 : 155 : pcxt->seg = dsm_create(segsize, DSM_CREATE_NULL_IF_MAXSEGMENTS);
329 [ + - ]: 155 : if (pcxt->seg != NULL)
330 : 155 : pcxt->toc = shm_toc_create(PARALLEL_MAGIC,
331 : 155 : dsm_segment_address(pcxt->seg),
332 : 155 : segsize);
333 : : else
334 : : {
335 : 0 : pcxt->nworkers = 0;
336 : 0 : pcxt->private_memory = MemoryContextAlloc(TopMemoryContext, segsize);
337 : 0 : pcxt->toc = shm_toc_create(PARALLEL_MAGIC, pcxt->private_memory,
338 : 0 : segsize);
339 : : }
340 : :
341 : : /* Initialize fixed-size state in shared memory. */
342 : 155 : fps = (FixedParallelState *)
343 : 155 : shm_toc_allocate(pcxt->toc, sizeof(FixedParallelState));
344 : 155 : fps->database_id = MyDatabaseId;
345 : 155 : fps->authenticated_user_id = GetAuthenticatedUserId();
346 : 155 : fps->session_user_id = GetSessionUserId();
347 : 155 : fps->outer_user_id = GetCurrentRoleId();
348 : 155 : GetUserIdAndSecContext(&fps->current_user_id, &fps->sec_context);
349 : 155 : fps->session_user_is_superuser = GetSessionUserIsSuperuser();
350 : 155 : fps->role_is_superuser = current_role_is_superuser;
351 : 310 : GetTempNamespaceState(&fps->temp_namespace_id,
352 : 155 : &fps->temp_toast_namespace_id);
353 : 155 : fps->parallel_leader_pgproc = MyProc;
354 : 155 : fps->parallel_leader_pid = MyProcPid;
355 : 155 : fps->parallel_leader_proc_number = MyProcNumber;
356 : 155 : fps->xact_ts = GetCurrentTransactionStartTimestamp();
357 : 155 : fps->stmt_ts = GetCurrentStatementStartTimestamp();
358 : 155 : fps->serializable_xact_handle = ShareSerializableXact();
359 : 155 : SpinLockInit(&fps->mutex);
360 : 155 : fps->last_xlog_end = 0;
361 : 155 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_FIXED, fps);
362 : :
363 : : /* We can skip the rest of this if we're not budgeting for any workers. */
364 [ + - ]: 155 : if (pcxt->nworkers > 0)
365 : : {
366 : 155 : char *libraryspace;
367 : 155 : char *gucspace;
368 : 155 : char *combocidspace;
369 : 155 : char *tsnapspace;
370 : 155 : char *asnapspace;
371 : 155 : char *tstatespace;
372 : 155 : char *pendingsyncsspace;
373 : 155 : char *reindexspace;
374 : 155 : char *relmapperspace;
375 : 155 : char *error_queue_space;
376 : 155 : char *session_dsm_handle_space;
377 : 155 : char *entrypointstate;
378 : 155 : char *uncommittedenumsspace;
379 : 155 : char *clientconninfospace;
380 : 155 : Size lnamelen;
381 : :
382 : : /* Serialize shared libraries we have loaded. */
383 : 155 : libraryspace = shm_toc_allocate(pcxt->toc, library_len);
384 : 155 : SerializeLibraryState(library_len, libraryspace);
385 : 155 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_LIBRARY, libraryspace);
386 : :
387 : : /* Serialize GUC settings. */
388 : 155 : gucspace = shm_toc_allocate(pcxt->toc, guc_len);
389 : 155 : SerializeGUCState(guc_len, gucspace);
390 : 155 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_GUC, gucspace);
391 : :
392 : : /* Serialize combo CID state. */
393 : 155 : combocidspace = shm_toc_allocate(pcxt->toc, combocidlen);
394 : 155 : SerializeComboCIDState(combocidlen, combocidspace);
395 : 155 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_COMBO_CID, combocidspace);
396 : :
397 : : /*
398 : : * Serialize the transaction snapshot if the transaction isolation
399 : : * level uses a transaction snapshot.
400 : : */
401 [ + - ]: 155 : if (IsolationUsesXactSnapshot())
402 : : {
403 : 0 : tsnapspace = shm_toc_allocate(pcxt->toc, tsnaplen);
404 : 0 : SerializeSnapshot(transaction_snapshot, tsnapspace);
405 : 0 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_TRANSACTION_SNAPSHOT,
406 : 0 : tsnapspace);
407 : 0 : }
408 : :
409 : : /* Serialize the active snapshot. */
410 : 155 : asnapspace = shm_toc_allocate(pcxt->toc, asnaplen);
411 : 155 : SerializeSnapshot(active_snapshot, asnapspace);
412 : 155 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_ACTIVE_SNAPSHOT, asnapspace);
413 : :
414 : : /* Provide the handle for per-session segment. */
415 : 155 : session_dsm_handle_space = shm_toc_allocate(pcxt->toc,
416 : : sizeof(dsm_handle));
417 : 155 : *(dsm_handle *) session_dsm_handle_space = session_dsm_handle;
418 : 310 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_SESSION_DSM,
419 : 155 : session_dsm_handle_space);
420 : :
421 : : /* Serialize transaction state. */
422 : 155 : tstatespace = shm_toc_allocate(pcxt->toc, tstatelen);
423 : 155 : SerializeTransactionState(tstatelen, tstatespace);
424 : 155 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_TRANSACTION_STATE, tstatespace);
425 : :
426 : : /* Serialize pending syncs. */
427 : 155 : pendingsyncsspace = shm_toc_allocate(pcxt->toc, pendingsyncslen);
428 : 155 : SerializePendingSyncs(pendingsyncslen, pendingsyncsspace);
429 : 310 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_PENDING_SYNCS,
430 : 155 : pendingsyncsspace);
431 : :
432 : : /* Serialize reindex state. */
433 : 155 : reindexspace = shm_toc_allocate(pcxt->toc, reindexlen);
434 : 155 : SerializeReindexState(reindexlen, reindexspace);
435 : 155 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_REINDEX_STATE, reindexspace);
436 : :
437 : : /* Serialize relmapper state. */
438 : 155 : relmapperspace = shm_toc_allocate(pcxt->toc, relmapperlen);
439 : 155 : SerializeRelationMap(relmapperlen, relmapperspace);
440 : 310 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_RELMAPPER_STATE,
441 : 155 : relmapperspace);
442 : :
443 : : /* Serialize uncommitted enum state. */
444 : 310 : uncommittedenumsspace = shm_toc_allocate(pcxt->toc,
445 : 155 : uncommittedenumslen);
446 : 155 : SerializeUncommittedEnums(uncommittedenumsspace, uncommittedenumslen);
447 : 310 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_UNCOMMITTEDENUMS,
448 : 155 : uncommittedenumsspace);
449 : :
450 : : /* Serialize our ClientConnectionInfo. */
451 : 155 : clientconninfospace = shm_toc_allocate(pcxt->toc, clientconninfolen);
452 : 155 : SerializeClientConnectionInfo(clientconninfolen, clientconninfospace);
453 : 310 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_CLIENTCONNINFO,
454 : 155 : clientconninfospace);
455 : :
456 : : /* Allocate space for worker information. */
457 : 155 : pcxt->worker = palloc0_array(ParallelWorkerInfo, pcxt->nworkers);
458 : :
459 : : /*
460 : : * Establish error queues in dynamic shared memory.
461 : : *
462 : : * These queues should be used only for transmitting ErrorResponse,
463 : : * NoticeResponse, and NotifyResponse protocol messages. Tuple data
464 : : * should be transmitted via separate (possibly larger?) queues.
465 : : */
466 : 155 : error_queue_space =
467 : 310 : shm_toc_allocate(pcxt->toc,
468 : 155 : mul_size(PARALLEL_ERROR_QUEUE_SIZE,
469 : 155 : pcxt->nworkers));
470 [ + + ]: 503 : for (i = 0; i < pcxt->nworkers; ++i)
471 : : {
472 : 348 : char *start;
473 : 348 : shm_mq *mq;
474 : :
475 : 348 : start = error_queue_space + i * PARALLEL_ERROR_QUEUE_SIZE;
476 : 348 : mq = shm_mq_create(start, PARALLEL_ERROR_QUEUE_SIZE);
477 : 348 : shm_mq_set_receiver(mq, MyProc);
478 : 348 : pcxt->worker[i].error_mqh = shm_mq_attach(mq, pcxt->seg, NULL);
479 : 348 : }
480 : 155 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_ERROR_QUEUE, error_queue_space);
481 : :
482 : : /*
483 : : * Serialize entrypoint information. It's unsafe to pass function
484 : : * pointers across processes, as the function pointer may be different
485 : : * in each process in EXEC_BACKEND builds, so we always pass library
486 : : * and function name. (We use library name "postgres" for functions
487 : : * in the core backend.)
488 : : */
489 : 155 : lnamelen = strlen(pcxt->library_name);
490 : 465 : entrypointstate = shm_toc_allocate(pcxt->toc, lnamelen +
491 : 310 : strlen(pcxt->function_name) + 2);
492 : 155 : strcpy(entrypointstate, pcxt->library_name);
493 : 155 : strcpy(entrypointstate + lnamelen + 1, pcxt->function_name);
494 : 155 : shm_toc_insert(pcxt->toc, PARALLEL_KEY_ENTRYPOINT, entrypointstate);
495 : 155 : }
496 : :
497 : : /* Update nworkers_to_launch, in case we changed nworkers above. */
498 : 155 : pcxt->nworkers_to_launch = pcxt->nworkers;
499 : :
500 : : /* Restore previous memory context. */
501 : 155 : MemoryContextSwitchTo(oldcontext);
502 : 155 : }
503 : :
504 : : /*
505 : : * Reinitialize the dynamic shared memory segment for a parallel context such
506 : : * that we could launch workers for it again.
507 : : */
508 : : void
509 : 48 : ReinitializeParallelDSM(ParallelContext *pcxt)
510 : : {
511 : 48 : MemoryContext oldcontext;
512 : 48 : FixedParallelState *fps;
513 : :
514 : : /* We might be running in a very short-lived memory context. */
515 : 48 : oldcontext = MemoryContextSwitchTo(TopTransactionContext);
516 : :
517 : : /* Wait for any old workers to exit. */
518 [ + - ]: 48 : if (pcxt->nworkers_launched > 0)
519 : : {
520 : 48 : WaitForParallelWorkersToFinish(pcxt);
521 : 48 : WaitForParallelWorkersToExit(pcxt);
522 : 48 : pcxt->nworkers_launched = 0;
523 [ - + ]: 48 : if (pcxt->known_attached_workers)
524 : : {
525 : 48 : pfree(pcxt->known_attached_workers);
526 : 48 : pcxt->known_attached_workers = NULL;
527 : 48 : pcxt->nknown_attached_workers = 0;
528 : 48 : }
529 : 48 : }
530 : :
531 : : /* Reset a few bits of fixed parallel state to a clean state. */
532 : 48 : fps = shm_toc_lookup(pcxt->toc, PARALLEL_KEY_FIXED, false);
533 : 48 : fps->last_xlog_end = 0;
534 : :
535 : : /* Recreate error queues (if they exist). */
536 [ + - ]: 48 : if (pcxt->nworkers > 0)
537 : : {
538 : 48 : char *error_queue_space;
539 : 48 : int i;
540 : :
541 : 48 : error_queue_space =
542 : 48 : shm_toc_lookup(pcxt->toc, PARALLEL_KEY_ERROR_QUEUE, false);
543 [ + + ]: 191 : for (i = 0; i < pcxt->nworkers; ++i)
544 : : {
545 : 143 : char *start;
546 : 143 : shm_mq *mq;
547 : :
548 : 143 : start = error_queue_space + i * PARALLEL_ERROR_QUEUE_SIZE;
549 : 143 : mq = shm_mq_create(start, PARALLEL_ERROR_QUEUE_SIZE);
550 : 143 : shm_mq_set_receiver(mq, MyProc);
551 : 143 : pcxt->worker[i].error_mqh = shm_mq_attach(mq, pcxt->seg, NULL);
552 : 143 : }
553 : 48 : }
554 : :
555 : : /* Restore previous memory context. */
556 : 48 : MemoryContextSwitchTo(oldcontext);
557 : 48 : }
558 : :
559 : : /*
560 : : * Reinitialize parallel workers for a parallel context such that we could
561 : : * launch a different number of workers. This is required for cases where
562 : : * we need to reuse the same DSM segment, but the number of workers can
563 : : * vary from run-to-run.
564 : : */
565 : : void
566 : 11 : ReinitializeParallelWorkers(ParallelContext *pcxt, int nworkers_to_launch)
567 : : {
568 : : /*
569 : : * The number of workers that need to be launched must be less than the
570 : : * number of workers with which the parallel context is initialized. But
571 : : * the caller might not know that InitializeParallelDSM reduced nworkers,
572 : : * so just silently trim the request.
573 : : */
574 [ - + ]: 11 : pcxt->nworkers_to_launch = Min(pcxt->nworkers, nworkers_to_launch);
575 : 11 : }
576 : :
577 : : /*
578 : : * Launch parallel workers.
579 : : */
580 : : void
581 : 203 : LaunchParallelWorkers(ParallelContext *pcxt)
582 : : {
583 : 203 : MemoryContext oldcontext;
584 : 203 : BackgroundWorker worker;
585 : 203 : int i;
586 : 203 : bool any_registrations_failed = false;
587 : :
588 : : /* Skip this if we have no workers. */
589 [ + - - + ]: 203 : if (pcxt->nworkers == 0 || pcxt->nworkers_to_launch == 0)
590 : 0 : return;
591 : :
592 : : /* We need to be a lock group leader. */
593 : 203 : BecomeLockGroupLeader();
594 : :
595 : : /* If we do have workers, we'd better have a DSM segment. */
596 [ + - ]: 203 : Assert(pcxt->seg != NULL);
597 : :
598 : : /* We might be running in a short-lived memory context. */
599 : 203 : oldcontext = MemoryContextSwitchTo(TopTransactionContext);
600 : :
601 : : /* Configure a worker. */
602 : 203 : memset(&worker, 0, sizeof(worker));
603 : 406 : snprintf(worker.bgw_name, BGW_MAXLEN, "parallel worker for PID %d",
604 : 203 : MyProcPid);
605 : 203 : snprintf(worker.bgw_type, BGW_MAXLEN, "parallel worker");
606 : 203 : worker.bgw_flags =
607 : : BGWORKER_SHMEM_ACCESS | BGWORKER_BACKEND_DATABASE_CONNECTION
608 : : | BGWORKER_CLASS_PARALLEL;
609 : 203 : worker.bgw_start_time = BgWorkerStart_ConsistentState;
610 : 203 : worker.bgw_restart_time = BGW_NEVER_RESTART;
611 : 203 : sprintf(worker.bgw_library_name, "postgres");
612 : 203 : sprintf(worker.bgw_function_name, "ParallelWorkerMain");
613 : 203 : worker.bgw_main_arg = UInt32GetDatum(dsm_segment_handle(pcxt->seg));
614 : 203 : worker.bgw_notify_pid = MyProcPid;
615 : :
616 : : /*
617 : : * Start workers.
618 : : *
619 : : * The caller must be able to tolerate ending up with fewer workers than
620 : : * expected, so there is no need to throw an error here if registration
621 : : * fails. It wouldn't help much anyway, because registering the worker in
622 : : * no way guarantees that it will start up and initialize successfully.
623 : : */
624 [ + + ]: 693 : for (i = 0; i < pcxt->nworkers_to_launch; ++i)
625 : : {
626 : 490 : memcpy(worker.bgw_extra, &i, sizeof(int));
627 [ + + + + ]: 490 : if (!any_registrations_failed &&
628 : 481 : RegisterDynamicBackgroundWorker(&worker,
629 : 481 : &pcxt->worker[i].bgwhandle))
630 : : {
631 : 954 : shm_mq_set_handle(pcxt->worker[i].error_mqh,
632 : 477 : pcxt->worker[i].bgwhandle);
633 : 477 : pcxt->nworkers_launched++;
634 : 477 : }
635 : : else
636 : : {
637 : : /*
638 : : * If we weren't able to register the worker, then we've bumped up
639 : : * against the max_worker_processes limit, and future
640 : : * registrations will probably fail too, so arrange to skip them.
641 : : * But we still have to execute this code for the remaining slots
642 : : * to make sure that we forget about the error queues we budgeted
643 : : * for those workers. Otherwise, we'll wait for them to start,
644 : : * but they never will.
645 : : */
646 : 13 : any_registrations_failed = true;
647 : 13 : pcxt->worker[i].bgwhandle = NULL;
648 : 13 : shm_mq_detach(pcxt->worker[i].error_mqh);
649 : 13 : pcxt->worker[i].error_mqh = NULL;
650 : : }
651 : 490 : }
652 : :
653 : : /*
654 : : * Now that nworkers_launched has taken its final value, we can initialize
655 : : * known_attached_workers.
656 : : */
657 [ + + ]: 203 : if (pcxt->nworkers_launched > 0)
658 : : {
659 : 200 : pcxt->known_attached_workers = palloc0_array(bool, pcxt->nworkers_launched);
660 : 200 : pcxt->nknown_attached_workers = 0;
661 : 200 : }
662 : :
663 : : /* Restore previous memory context. */
664 : 203 : MemoryContextSwitchTo(oldcontext);
665 [ - + ]: 203 : }
666 : :
667 : : /*
668 : : * Wait for all workers to attach to their error queues, and throw an error if
669 : : * any worker fails to do this.
670 : : *
671 : : * Callers can assume that if this function returns successfully, then the
672 : : * number of workers given by pcxt->nworkers_launched have initialized and
673 : : * attached to their error queues. Whether or not these workers are guaranteed
674 : : * to still be running depends on what code the caller asked them to run;
675 : : * this function does not guarantee that they have not exited. However, it
676 : : * does guarantee that any workers which exited must have done so cleanly and
677 : : * after successfully performing the work with which they were tasked.
678 : : *
679 : : * If this function is not called, then some of the workers that were launched
680 : : * may not have been started due to a fork() failure, or may have exited during
681 : : * early startup prior to attaching to the error queue, so nworkers_launched
682 : : * cannot be viewed as completely reliable. It will never be less than the
683 : : * number of workers which actually started, but it might be more. Any workers
684 : : * that failed to start will still be discovered by
685 : : * WaitForParallelWorkersToFinish and an error will be thrown at that time,
686 : : * provided that function is eventually reached.
687 : : *
688 : : * In general, the leader process should do as much work as possible before
689 : : * calling this function. fork() failures and other early-startup failures
690 : : * are very uncommon, and having the leader sit idle when it could be doing
691 : : * useful work is undesirable. However, if the leader needs to wait for
692 : : * all of its workers or for a specific worker, it may want to call this
693 : : * function before doing so. If not, it must make some other provision for
694 : : * the failure-to-start case, lest it wait forever. On the other hand, a
695 : : * leader which never waits for a worker that might not be started yet, or
696 : : * at least never does so prior to WaitForParallelWorkersToFinish(), need not
697 : : * call this function at all.
698 : : */
699 : : void
700 : 28 : WaitForParallelWorkersToAttach(ParallelContext *pcxt)
701 : : {
702 : 28 : int i;
703 : :
704 : : /* Skip this if we have no launched workers. */
705 [ - + ]: 28 : if (pcxt->nworkers_launched == 0)
706 : 0 : return;
707 : :
708 : 823456 : for (;;)
709 : : {
710 : : /*
711 : : * This will process any parallel messages that are pending and it may
712 : : * also throw an error propagated from a worker.
713 : : */
714 [ + + ]: 823456 : CHECK_FOR_INTERRUPTS();
715 : :
716 [ + + ]: 1646912 : for (i = 0; i < pcxt->nworkers_launched; ++i)
717 : : {
718 : 823456 : BgwHandleStatus status;
719 : 823456 : shm_mq *mq;
720 : 823456 : int rc;
721 : 823456 : pid_t pid;
722 : :
723 [ + + ]: 823456 : if (pcxt->known_attached_workers[i])
724 : 4 : continue;
725 : :
726 : : /*
727 : : * If error_mqh is NULL, then the worker has already exited
728 : : * cleanly.
729 : : */
730 [ + - ]: 823452 : if (pcxt->worker[i].error_mqh == NULL)
731 : : {
732 : 0 : pcxt->known_attached_workers[i] = true;
733 : 0 : ++pcxt->nknown_attached_workers;
734 : 0 : continue;
735 : : }
736 : :
737 : 823452 : status = GetBackgroundWorkerPid(pcxt->worker[i].bgwhandle, &pid);
738 [ + + ]: 823452 : if (status == BGWH_STARTED)
739 : : {
740 : : /* Has the worker attached to the error queue? */
741 : 823436 : mq = shm_mq_get_queue(pcxt->worker[i].error_mqh);
742 [ + + ]: 823436 : if (shm_mq_get_sender(mq) != NULL)
743 : : {
744 : : /* Yes, so it is known to be attached. */
745 : 24 : pcxt->known_attached_workers[i] = true;
746 : 24 : ++pcxt->nknown_attached_workers;
747 : 24 : }
748 : 823436 : }
749 [ - + ]: 16 : else if (status == BGWH_STOPPED)
750 : : {
751 : : /*
752 : : * If the worker stopped without attaching to the error queue,
753 : : * throw an error.
754 : : */
755 : 0 : mq = shm_mq_get_queue(pcxt->worker[i].error_mqh);
756 [ # # ]: 0 : if (shm_mq_get_sender(mq) == NULL)
757 [ # # # # ]: 0 : ereport(ERROR,
758 : : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
759 : : errmsg("parallel worker failed to initialize"),
760 : : errhint("More details may be available in the server log.")));
761 : :
762 : 0 : pcxt->known_attached_workers[i] = true;
763 : 0 : ++pcxt->nknown_attached_workers;
764 : 0 : }
765 : : else
766 : : {
767 : : /*
768 : : * Worker not yet started, so we must wait. The postmaster
769 : : * will notify us if the worker's state changes. Our latch
770 : : * might also get set for some other reason, but if so we'll
771 : : * just end up waiting for the same worker again.
772 : : */
773 : 16 : rc = WaitLatch(MyLatch,
774 : : WL_LATCH_SET | WL_EXIT_ON_PM_DEATH,
775 : : -1, WAIT_EVENT_BGWORKER_STARTUP);
776 : :
777 [ - + ]: 16 : if (rc & WL_LATCH_SET)
778 : 16 : ResetLatch(MyLatch);
779 : : }
780 [ + + ]: 823456 : }
781 : :
782 : : /* If all workers are known to have started, we're done. */
783 [ + + ]: 823456 : if (pcxt->nknown_attached_workers >= pcxt->nworkers_launched)
784 : : {
785 [ + - ]: 28 : Assert(pcxt->nknown_attached_workers == pcxt->nworkers_launched);
786 : 28 : break;
787 : : }
788 : : }
789 : 28 : }
790 : :
791 : : /*
792 : : * Wait for all workers to finish computing.
793 : : *
794 : : * Even if the parallel operation seems to have completed successfully, it's
795 : : * important to call this function afterwards. We must not miss any errors
796 : : * the workers may have thrown during the parallel operation, or any that they
797 : : * may yet throw while shutting down.
798 : : *
799 : : * Also, we want to update our notion of XactLastRecEnd based on worker
800 : : * feedback.
801 : : */
802 : : void
803 : 249 : WaitForParallelWorkersToFinish(ParallelContext *pcxt)
804 : : {
805 : 378 : for (;;)
806 : : {
807 : 378 : bool anyone_alive = false;
808 : 378 : int nfinished = 0;
809 : 378 : int i;
810 : :
811 : : /*
812 : : * This will process any parallel messages that are pending, which may
813 : : * change the outcome of the loop that follows. It may also throw an
814 : : * error propagated from a worker.
815 : : */
816 [ + + ]: 378 : CHECK_FOR_INTERRUPTS();
817 : :
818 [ + + ]: 1296 : for (i = 0; i < pcxt->nworkers_launched; ++i)
819 : : {
820 : : /*
821 : : * If error_mqh is NULL, then the worker has already exited
822 : : * cleanly. If we have received a message through error_mqh from
823 : : * the worker, we know it started up cleanly, and therefore we're
824 : : * certain to be notified when it exits.
825 : : */
826 [ + + ]: 919 : if (pcxt->worker[i].error_mqh == NULL)
827 : 767 : ++nfinished;
828 [ + + ]: 152 : else if (pcxt->known_attached_workers[i])
829 : : {
830 : 1 : anyone_alive = true;
831 : 1 : break;
832 : : }
833 : 918 : }
834 : :
835 [ + + ]: 378 : if (!anyone_alive)
836 : : {
837 : : /* If all workers are known to have finished, we're done. */
838 [ + + ]: 377 : if (nfinished >= pcxt->nworkers_launched)
839 : : {
840 [ - + ]: 249 : Assert(nfinished == pcxt->nworkers_launched);
841 : 249 : break;
842 : : }
843 : :
844 : : /*
845 : : * We didn't detect any living workers, but not all workers are
846 : : * known to have exited cleanly. Either not all workers have
847 : : * launched yet, or maybe some of them failed to start or
848 : : * terminated abnormally.
849 : : */
850 [ + + ]: 429 : for (i = 0; i < pcxt->nworkers_launched; ++i)
851 : : {
852 : 301 : pid_t pid;
853 : 301 : shm_mq *mq;
854 : :
855 : : /*
856 : : * If the worker is BGWH_NOT_YET_STARTED or BGWH_STARTED, we
857 : : * should just keep waiting. If it is BGWH_STOPPED, then
858 : : * further investigation is needed.
859 : : */
860 [ + + ]: 301 : if (pcxt->worker[i].error_mqh == NULL ||
861 [ + - + - ]: 151 : pcxt->worker[i].bgwhandle == NULL ||
862 : 151 : GetBackgroundWorkerPid(pcxt->worker[i].bgwhandle,
863 : 151 : &pid) != BGWH_STOPPED)
864 : 301 : continue;
865 : :
866 : : /*
867 : : * Check whether the worker ended up stopped without ever
868 : : * attaching to the error queue. If so, the postmaster was
869 : : * unable to fork the worker or it exited without initializing
870 : : * properly. We must throw an error, since the caller may
871 : : * have been expecting the worker to do some work before
872 : : * exiting.
873 : : */
874 : 0 : mq = shm_mq_get_queue(pcxt->worker[i].error_mqh);
875 [ # # ]: 0 : if (shm_mq_get_sender(mq) == NULL)
876 [ # # # # ]: 0 : ereport(ERROR,
877 : : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
878 : : errmsg("parallel worker failed to initialize"),
879 : : errhint("More details may be available in the server log.")));
880 : :
881 : : /*
882 : : * The worker is stopped, but is attached to the error queue.
883 : : * Unless there's a bug somewhere, this will only happen when
884 : : * the worker writes messages and terminates after the
885 : : * CHECK_FOR_INTERRUPTS() near the top of this function and
886 : : * before the call to GetBackgroundWorkerPid(). In that case,
887 : : * our latch should have been set as well and the right things
888 : : * will happen on the next pass through the loop.
889 : : */
890 [ + - ]: 301 : }
891 : 128 : }
892 : :
893 : 129 : (void) WaitLatch(MyLatch, WL_LATCH_SET | WL_EXIT_ON_PM_DEATH, -1,
894 : : WAIT_EVENT_PARALLEL_FINISH);
895 : 129 : ResetLatch(MyLatch);
896 [ + + ]: 378 : }
897 : :
898 [ - + ]: 249 : if (pcxt->toc != NULL)
899 : : {
900 : 249 : FixedParallelState *fps;
901 : :
902 : 249 : fps = shm_toc_lookup(pcxt->toc, PARALLEL_KEY_FIXED, false);
903 [ + + ]: 249 : if (fps->last_xlog_end > XactLastRecEnd)
904 : 5 : XactLastRecEnd = fps->last_xlog_end;
905 : 249 : }
906 : 249 : }
907 : :
908 : : /*
909 : : * Wait for all workers to exit.
910 : : *
911 : : * This function ensures that workers have been completely shutdown. The
912 : : * difference between WaitForParallelWorkersToFinish and this function is
913 : : * that the former just ensures that last message sent by a worker backend is
914 : : * received by the leader backend whereas this ensures the complete shutdown.
915 : : */
916 : : static void
917 : 203 : WaitForParallelWorkersToExit(ParallelContext *pcxt)
918 : : {
919 : 203 : int i;
920 : :
921 : : /* Wait until the workers actually die. */
922 [ + + ]: 680 : for (i = 0; i < pcxt->nworkers_launched; ++i)
923 : : {
924 : 477 : BgwHandleStatus status;
925 : :
926 [ + - - + ]: 477 : if (pcxt->worker == NULL || pcxt->worker[i].bgwhandle == NULL)
927 : 0 : continue;
928 : :
929 : 477 : status = WaitForBackgroundWorkerShutdown(pcxt->worker[i].bgwhandle);
930 : :
931 : : /*
932 : : * If the postmaster kicked the bucket, we have no chance of cleaning
933 : : * up safely -- we won't be able to tell when our workers are actually
934 : : * dead. This doesn't necessitate a PANIC since they will all abort
935 : : * eventually, but we can't safely continue this session.
936 : : */
937 [ + - ]: 477 : if (status == BGWH_POSTMASTER_DIED)
938 [ # # # # ]: 0 : ereport(FATAL,
939 : : (errcode(ERRCODE_ADMIN_SHUTDOWN),
940 : : errmsg("postmaster exited during a parallel transaction")));
941 : :
942 : : /* Release memory. */
943 : 477 : pfree(pcxt->worker[i].bgwhandle);
944 : 477 : pcxt->worker[i].bgwhandle = NULL;
945 [ - - + ]: 477 : }
946 : 203 : }
947 : :
948 : : /*
949 : : * Destroy a parallel context.
950 : : *
951 : : * If expecting a clean exit, you should use WaitForParallelWorkersToFinish()
952 : : * first, before calling this function. When this function is invoked, any
953 : : * remaining workers are forcibly killed; the dynamic shared memory segment
954 : : * is unmapped; and we then wait (uninterruptibly) for the workers to exit.
955 : : */
956 : : void
957 : 155 : DestroyParallelContext(ParallelContext *pcxt)
958 : : {
959 : 155 : int i;
960 : :
961 : : /*
962 : : * Be careful about order of operations here! We remove the parallel
963 : : * context from the list before we do anything else; otherwise, if an
964 : : * error occurs during a subsequent step, we might try to nuke it again
965 : : * from AtEOXact_Parallel or AtEOSubXact_Parallel.
966 : : */
967 : 155 : dlist_delete(&pcxt->node);
968 : :
969 : : /* Kill each worker in turn, and forget their error queues. */
970 [ + - ]: 155 : if (pcxt->worker != NULL)
971 : : {
972 [ + + ]: 490 : for (i = 0; i < pcxt->nworkers_launched; ++i)
973 : : {
974 [ + + ]: 335 : if (pcxt->worker[i].error_mqh != NULL)
975 : : {
976 : 2 : TerminateBackgroundWorker(pcxt->worker[i].bgwhandle);
977 : :
978 : 2 : shm_mq_detach(pcxt->worker[i].error_mqh);
979 : 2 : pcxt->worker[i].error_mqh = NULL;
980 : 2 : }
981 : 335 : }
982 : 155 : }
983 : :
984 : : /*
985 : : * If we have allocated a shared memory segment, detach it. This will
986 : : * implicitly detach the error queues, and any other shared memory queues,
987 : : * stored there.
988 : : */
989 [ + - ]: 155 : if (pcxt->seg != NULL)
990 : : {
991 : 155 : dsm_detach(pcxt->seg);
992 : 155 : pcxt->seg = NULL;
993 : 155 : }
994 : :
995 : : /*
996 : : * If this parallel context is actually in backend-private memory rather
997 : : * than shared memory, free that memory instead.
998 : : */
999 [ - + ]: 155 : if (pcxt->private_memory != NULL)
1000 : : {
1001 : 0 : pfree(pcxt->private_memory);
1002 : 0 : pcxt->private_memory = NULL;
1003 : 0 : }
1004 : :
1005 : : /*
1006 : : * We can't finish transaction commit or abort until all of the workers
1007 : : * have exited. This means, in particular, that we can't respond to
1008 : : * interrupts at this stage.
1009 : : */
1010 : 155 : HOLD_INTERRUPTS();
1011 : 155 : WaitForParallelWorkersToExit(pcxt);
1012 [ + - ]: 155 : RESUME_INTERRUPTS();
1013 : :
1014 : : /* Free the worker array itself. */
1015 [ - + ]: 155 : if (pcxt->worker != NULL)
1016 : : {
1017 : 155 : pfree(pcxt->worker);
1018 : 155 : pcxt->worker = NULL;
1019 : 155 : }
1020 : :
1021 : : /* Free memory. */
1022 : 155 : pfree(pcxt->library_name);
1023 : 155 : pfree(pcxt->function_name);
1024 : 155 : pfree(pcxt);
1025 : 155 : }
1026 : :
1027 : : /*
1028 : : * Are there any parallel contexts currently active?
1029 : : */
1030 : : bool
1031 : 57110 : ParallelContextActive(void)
1032 : : {
1033 : 57110 : return !dlist_is_empty(&pcxt_list);
1034 : : }
1035 : :
1036 : : /*
1037 : : * Handle receipt of an interrupt indicating a parallel worker message.
1038 : : *
1039 : : * Note: this is called within a signal handler! All we can do is set
1040 : : * a flag that will cause the next CHECK_FOR_INTERRUPTS() to invoke
1041 : : * ProcessParallelMessages().
1042 : : */
1043 : : void
1044 : 416 : HandleParallelMessageInterrupt(void)
1045 : : {
1046 : 416 : InterruptPending = true;
1047 : 416 : ParallelMessagePending = true;
1048 : 416 : SetLatch(MyLatch);
1049 : 416 : }
1050 : :
1051 : : /*
1052 : : * Process any queued protocol messages received from parallel workers.
1053 : : */
1054 : : void
1055 : 408 : ProcessParallelMessages(void)
1056 : : {
1057 : 408 : dlist_iter iter;
1058 : 408 : MemoryContext oldcontext;
1059 : :
1060 : : static MemoryContext hpm_context = NULL;
1061 : :
1062 : : /*
1063 : : * This is invoked from ProcessInterrupts(), and since some of the
1064 : : * functions it calls contain CHECK_FOR_INTERRUPTS(), there is a potential
1065 : : * for recursive calls if more signals are received while this runs. It's
1066 : : * unclear that recursive entry would be safe, and it doesn't seem useful
1067 : : * even if it is safe, so let's block interrupts until done.
1068 : : */
1069 : 408 : HOLD_INTERRUPTS();
1070 : :
1071 : : /*
1072 : : * Moreover, CurrentMemoryContext might be pointing almost anywhere. We
1073 : : * don't want to risk leaking data into long-lived contexts, so let's do
1074 : : * our work here in a private context that we can reset on each use.
1075 : : */
1076 [ + + ]: 408 : if (hpm_context == NULL) /* first time through? */
1077 : 22 : hpm_context = AllocSetContextCreate(TopMemoryContext,
1078 : : "ProcessParallelMessages",
1079 : : ALLOCSET_DEFAULT_SIZES);
1080 : : else
1081 : 386 : MemoryContextReset(hpm_context);
1082 : :
1083 : 408 : oldcontext = MemoryContextSwitchTo(hpm_context);
1084 : :
1085 : : /* OK to process messages. Reset the flag saying there are more to do. */
1086 : 408 : ParallelMessagePending = false;
1087 : :
1088 [ + - + + ]: 855 : dlist_foreach(iter, &pcxt_list)
1089 : : {
1090 : 447 : ParallelContext *pcxt;
1091 : 447 : int i;
1092 : :
1093 : 447 : pcxt = dlist_container(ParallelContext, node, iter.cur);
1094 [ - + ]: 447 : if (pcxt->worker == NULL)
1095 : 0 : continue;
1096 : :
1097 [ + + ]: 1761 : for (i = 0; i < pcxt->nworkers_launched; ++i)
1098 : : {
1099 : : /*
1100 : : * Read as many messages as we can from each worker, but stop when
1101 : : * either (1) the worker's error queue goes away, which can happen
1102 : : * if we receive a Terminate message from the worker; or (2) no
1103 : : * more messages can be read from the worker without blocking.
1104 : : */
1105 [ + + ]: 1789 : while (pcxt->worker[i].error_mqh != NULL)
1106 : : {
1107 : 785 : shm_mq_result res;
1108 : 785 : Size nbytes;
1109 : 785 : void *data;
1110 : :
1111 : 785 : res = shm_mq_receive(pcxt->worker[i].error_mqh, &nbytes,
1112 : : &data, true);
1113 [ + + ]: 785 : if (res == SHM_MQ_WOULD_BLOCK)
1114 : 310 : break;
1115 [ + - ]: 475 : else if (res == SHM_MQ_SUCCESS)
1116 : : {
1117 : 475 : StringInfoData msg;
1118 : :
1119 : 475 : initStringInfo(&msg);
1120 : 475 : appendBinaryStringInfo(&msg, data, nbytes);
1121 : 475 : ProcessParallelMessage(pcxt, i, &msg);
1122 : 475 : pfree(msg.data);
1123 : 475 : }
1124 : : else
1125 [ # # # # ]: 0 : ereport(ERROR,
1126 : : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
1127 : : errmsg("lost connection to parallel worker")));
1128 [ + + ]: 785 : }
1129 : 1314 : }
1130 [ - + ]: 447 : }
1131 : :
1132 : 408 : MemoryContextSwitchTo(oldcontext);
1133 : :
1134 : : /* Might as well clear the context on our way out */
1135 : 408 : MemoryContextReset(hpm_context);
1136 : :
1137 [ + - ]: 408 : RESUME_INTERRUPTS();
1138 : 408 : }
1139 : :
1140 : : /*
1141 : : * Process a single protocol message received from a single parallel worker.
1142 : : */
1143 : : static void
1144 : 477 : ProcessParallelMessage(ParallelContext *pcxt, int i, StringInfo msg)
1145 : : {
1146 : 477 : char msgtype;
1147 : :
1148 [ + - + + ]: 477 : if (pcxt->known_attached_workers != NULL &&
1149 : 477 : !pcxt->known_attached_workers[i])
1150 : : {
1151 : 453 : pcxt->known_attached_workers[i] = true;
1152 : 453 : pcxt->nknown_attached_workers++;
1153 : 453 : }
1154 : :
1155 : 477 : msgtype = pq_getmsgbyte(msg);
1156 : :
1157 [ + - - + : 477 : switch (msgtype)
- ]
1158 : : {
1159 : : case PqMsg_ErrorResponse:
1160 : : case PqMsg_NoticeResponse:
1161 : : {
1162 : 2 : ErrorData edata;
1163 : 2 : ErrorContextCallback *save_error_context_stack;
1164 : :
1165 : : /* Parse ErrorResponse or NoticeResponse. */
1166 : 2 : pq_parse_errornotice(msg, &edata);
1167 : :
1168 : : /* Death of a worker isn't enough justification for suicide. */
1169 [ - + ]: 2 : edata.elevel = Min(edata.elevel, ERROR);
1170 : :
1171 : : /*
1172 : : * If desired, add a context line to show that this is a
1173 : : * message propagated from a parallel worker. Otherwise, it
1174 : : * can sometimes be confusing to understand what actually
1175 : : * happened. (We don't do this in DEBUG_PARALLEL_REGRESS mode
1176 : : * because it causes test-result instability depending on
1177 : : * whether a parallel worker is actually used or not.)
1178 : : */
1179 [ - + ]: 2 : if (debug_parallel_query != DEBUG_PARALLEL_REGRESS)
1180 : : {
1181 [ + + ]: 2 : if (edata.context)
1182 : 2 : edata.context = psprintf("%s\n%s", edata.context,
1183 : 1 : _("parallel worker"));
1184 : : else
1185 : 1 : edata.context = pstrdup(_("parallel worker"));
1186 : 2 : }
1187 : :
1188 : : /*
1189 : : * Context beyond that should use the error context callbacks
1190 : : * that were in effect when the ParallelContext was created,
1191 : : * not the current ones.
1192 : : */
1193 : 2 : save_error_context_stack = error_context_stack;
1194 : 2 : error_context_stack = pcxt->error_context_stack;
1195 : :
1196 : : /* Rethrow error or print notice. */
1197 : 2 : ThrowErrorData(&edata);
1198 : :
1199 : : /* Not an error, so restore previous context stack. */
1200 : 2 : error_context_stack = save_error_context_stack;
1201 : :
1202 : : break;
1203 : 2 : }
1204 : :
1205 : : case PqMsg_NotificationResponse:
1206 : : {
1207 : : /* Propagate NotifyResponse. */
1208 : 0 : int32 pid;
1209 : 0 : const char *channel;
1210 : 0 : const char *payload;
1211 : :
1212 : 0 : pid = pq_getmsgint(msg, 4);
1213 : 0 : channel = pq_getmsgrawstring(msg);
1214 : 0 : payload = pq_getmsgrawstring(msg);
1215 : 0 : pq_endmessage(msg);
1216 : :
1217 : 0 : NotifyMyFrontEnd(channel, payload, pid);
1218 : :
1219 : : break;
1220 : 0 : }
1221 : :
1222 : : case PqMsg_Progress:
1223 : : {
1224 : : /*
1225 : : * Only incremental progress reporting is currently supported.
1226 : : * However, it's possible to add more fields to the message to
1227 : : * allow for handling of other backend progress APIs.
1228 : : */
1229 : 0 : int index = pq_getmsgint(msg, 4);
1230 : 0 : int64 incr = pq_getmsgint64(msg);
1231 : :
1232 : 0 : pq_getmsgend(msg);
1233 : :
1234 : 0 : pgstat_progress_incr_param(index, incr);
1235 : :
1236 : : break;
1237 : 0 : }
1238 : :
1239 : : case PqMsg_Terminate:
1240 : : {
1241 : 475 : shm_mq_detach(pcxt->worker[i].error_mqh);
1242 : 475 : pcxt->worker[i].error_mqh = NULL;
1243 : 475 : break;
1244 : : }
1245 : :
1246 : : default:
1247 : : {
1248 [ # # # # ]: 0 : elog(ERROR, "unrecognized message type received from parallel worker: %c (message length %d bytes)",
1249 : : msgtype, msg->len);
1250 : : }
1251 : 0 : }
1252 : 477 : }
1253 : :
1254 : : /*
1255 : : * End-of-subtransaction cleanup for parallel contexts.
1256 : : *
1257 : : * Here we remove only parallel contexts initiated within the current
1258 : : * subtransaction.
1259 : : */
1260 : : void
1261 : 1665 : AtEOSubXact_Parallel(bool isCommit, SubTransactionId mySubId)
1262 : : {
1263 [ + + ]: 1666 : while (!dlist_is_empty(&pcxt_list))
1264 : : {
1265 : 1 : ParallelContext *pcxt;
1266 : :
1267 : 1 : pcxt = dlist_head_element(ParallelContext, node, &pcxt_list);
1268 [ - + ]: 1 : if (pcxt->subid != mySubId)
1269 : 0 : break;
1270 [ + - ]: 1 : if (isCommit)
1271 [ # # # # ]: 0 : elog(WARNING, "leaked parallel context");
1272 : 1 : DestroyParallelContext(pcxt);
1273 [ - - + ]: 1 : }
1274 : 1665 : }
1275 : :
1276 : : /*
1277 : : * End-of-transaction cleanup for parallel contexts.
1278 : : *
1279 : : * We nuke all remaining parallel contexts.
1280 : : */
1281 : : void
1282 : 57918 : AtEOXact_Parallel(bool isCommit)
1283 : : {
1284 [ + + ]: 57919 : while (!dlist_is_empty(&pcxt_list))
1285 : : {
1286 : 1 : ParallelContext *pcxt;
1287 : :
1288 : 1 : pcxt = dlist_head_element(ParallelContext, node, &pcxt_list);
1289 [ + - ]: 1 : if (isCommit)
1290 [ # # # # ]: 0 : elog(WARNING, "leaked parallel context");
1291 : 1 : DestroyParallelContext(pcxt);
1292 : 1 : }
1293 : 57918 : }
1294 : :
1295 : : /*
1296 : : * Main entrypoint for parallel workers.
1297 : : */
1298 : : void
1299 : 477 : ParallelWorkerMain(Datum main_arg)
1300 : : {
1301 : 477 : dsm_segment *seg;
1302 : 477 : shm_toc *toc;
1303 : 477 : FixedParallelState *fps;
1304 : 477 : char *error_queue_space;
1305 : 477 : shm_mq *mq;
1306 : 477 : shm_mq_handle *mqh;
1307 : 477 : char *libraryspace;
1308 : 477 : char *entrypointstate;
1309 : 477 : char *library_name;
1310 : 477 : char *function_name;
1311 : 477 : parallel_worker_main_type entrypt;
1312 : 477 : char *gucspace;
1313 : 477 : char *combocidspace;
1314 : 477 : char *tsnapspace;
1315 : 477 : char *asnapspace;
1316 : 477 : char *tstatespace;
1317 : 477 : char *pendingsyncsspace;
1318 : 477 : char *reindexspace;
1319 : 477 : char *relmapperspace;
1320 : 477 : char *uncommittedenumsspace;
1321 : 477 : char *clientconninfospace;
1322 : 477 : char *session_dsm_handle_space;
1323 : 477 : Snapshot tsnapshot;
1324 : 477 : Snapshot asnapshot;
1325 : :
1326 : : /* Set flag to indicate that we're initializing a parallel worker. */
1327 : 477 : InitializingParallelWorker = true;
1328 : :
1329 : : /* Establish signal handlers. */
1330 : 477 : pqsignal(SIGTERM, die);
1331 : 477 : BackgroundWorkerUnblockSignals();
1332 : :
1333 : : /* Determine and set our parallel worker number. */
1334 [ + - ]: 477 : Assert(ParallelWorkerNumber == -1);
1335 : 477 : memcpy(&ParallelWorkerNumber, MyBgworkerEntry->bgw_extra, sizeof(int));
1336 : :
1337 : : /* Set up a memory context to work in, just for cleanliness. */
1338 : 477 : CurrentMemoryContext = AllocSetContextCreate(TopMemoryContext,
1339 : : "Parallel worker",
1340 : : ALLOCSET_DEFAULT_SIZES);
1341 : :
1342 : : /*
1343 : : * Attach to the dynamic shared memory segment for the parallel query, and
1344 : : * find its table of contents.
1345 : : *
1346 : : * Note: at this point, we have not created any ResourceOwner in this
1347 : : * process. This will result in our DSM mapping surviving until process
1348 : : * exit, which is fine. If there were a ResourceOwner, it would acquire
1349 : : * ownership of the mapping, but we have no need for that.
1350 : : */
1351 : 477 : seg = dsm_attach(DatumGetUInt32(main_arg));
1352 [ + - ]: 477 : if (seg == NULL)
1353 [ # # # # ]: 0 : ereport(ERROR,
1354 : : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
1355 : : errmsg("could not map dynamic shared memory segment")));
1356 : 477 : toc = shm_toc_attach(PARALLEL_MAGIC, dsm_segment_address(seg));
1357 [ + - ]: 477 : if (toc == NULL)
1358 [ # # # # ]: 0 : ereport(ERROR,
1359 : : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
1360 : : errmsg("invalid magic number in dynamic shared memory segment")));
1361 : :
1362 : : /* Look up fixed parallel state. */
1363 : 477 : fps = shm_toc_lookup(toc, PARALLEL_KEY_FIXED, false);
1364 : 477 : MyFixedParallelState = fps;
1365 : :
1366 : : /* Arrange to signal the leader if we exit. */
1367 : 477 : ParallelLeaderPid = fps->parallel_leader_pid;
1368 : 477 : ParallelLeaderProcNumber = fps->parallel_leader_proc_number;
1369 : 477 : before_shmem_exit(ParallelWorkerShutdown, PointerGetDatum(seg));
1370 : :
1371 : : /*
1372 : : * Now we can find and attach to the error queue provided for us. That's
1373 : : * good, because until we do that, any errors that happen here will not be
1374 : : * reported back to the process that requested that this worker be
1375 : : * launched.
1376 : : */
1377 : 477 : error_queue_space = shm_toc_lookup(toc, PARALLEL_KEY_ERROR_QUEUE, false);
1378 : 954 : mq = (shm_mq *) (error_queue_space +
1379 : 477 : ParallelWorkerNumber * PARALLEL_ERROR_QUEUE_SIZE);
1380 : 477 : shm_mq_set_sender(mq, MyProc);
1381 : 477 : mqh = shm_mq_attach(mq, seg, NULL);
1382 : 477 : pq_redirect_to_shm_mq(seg, mqh);
1383 : 954 : pq_set_parallel_leader(fps->parallel_leader_pid,
1384 : 477 : fps->parallel_leader_proc_number);
1385 : :
1386 : : /*
1387 : : * Hooray! Primary initialization is complete. Now, we need to set up our
1388 : : * backend-local state to match the original backend.
1389 : : */
1390 : :
1391 : : /*
1392 : : * Join locking group. We must do this before anything that could try to
1393 : : * acquire a heavyweight lock, because any heavyweight locks acquired to
1394 : : * this point could block either directly against the parallel group
1395 : : * leader or against some process which in turn waits for a lock that
1396 : : * conflicts with the parallel group leader, causing an undetected
1397 : : * deadlock. (If we can't join the lock group, the leader has gone away,
1398 : : * so just exit quietly.)
1399 : : */
1400 [ + - + - ]: 954 : if (!BecomeLockGroupMember(fps->parallel_leader_pgproc,
1401 : 477 : fps->parallel_leader_pid))
1402 : 0 : return;
1403 : :
1404 : : /*
1405 : : * Restore transaction and statement start-time timestamps. This must
1406 : : * happen before anything that would start a transaction, else asserts in
1407 : : * xact.c will fire.
1408 : : */
1409 : 477 : SetParallelStartTimestamps(fps->xact_ts, fps->stmt_ts);
1410 : :
1411 : : /*
1412 : : * Identify the entry point to be called. In theory this could result in
1413 : : * loading an additional library, though most likely the entry point is in
1414 : : * the core backend or in a library we just loaded.
1415 : : */
1416 : 477 : entrypointstate = shm_toc_lookup(toc, PARALLEL_KEY_ENTRYPOINT, false);
1417 : 477 : library_name = entrypointstate;
1418 : 477 : function_name = entrypointstate + strlen(library_name) + 1;
1419 : :
1420 : 477 : entrypt = LookupParallelWorkerFunction(library_name, function_name);
1421 : :
1422 : : /*
1423 : : * Restore current session authorization and role id. No verification
1424 : : * happens here, we just blindly adopt the leader's state. Note that this
1425 : : * has to happen before InitPostgres, since InitializeSessionUserId will
1426 : : * not set these variables.
1427 : : */
1428 : 477 : SetAuthenticatedUserId(fps->authenticated_user_id);
1429 : 954 : SetSessionAuthorization(fps->session_user_id,
1430 : 477 : fps->session_user_is_superuser);
1431 : 477 : SetCurrentRoleId(fps->outer_user_id, fps->role_is_superuser);
1432 : :
1433 : : /*
1434 : : * Restore database connection. We skip connection authorization checks,
1435 : : * reasoning that (a) the leader checked these things when it started, and
1436 : : * (b) we do not want parallel mode to cause these failures, because that
1437 : : * would make use of parallel query plans not transparent to applications.
1438 : : */
1439 : 954 : BackgroundWorkerInitializeConnectionByOid(fps->database_id,
1440 : 477 : fps->authenticated_user_id,
1441 : : BGWORKER_BYPASS_ALLOWCONN |
1442 : : BGWORKER_BYPASS_ROLELOGINCHECK);
1443 : :
1444 : : /*
1445 : : * Set the client encoding to the database encoding, since that is what
1446 : : * the leader will expect. (We're cheating a bit by not calling
1447 : : * PrepareClientEncoding first. It's okay because this call will always
1448 : : * result in installing a no-op conversion. No error should be possible,
1449 : : * but check anyway.)
1450 : : */
1451 [ + - ]: 477 : if (SetClientEncoding(GetDatabaseEncoding()) < 0)
1452 [ # # # # ]: 0 : elog(ERROR, "SetClientEncoding(%d) failed", GetDatabaseEncoding());
1453 : :
1454 : : /*
1455 : : * Load libraries that were loaded by original backend. We want to do
1456 : : * this before restoring GUCs, because the libraries might define custom
1457 : : * variables.
1458 : : */
1459 : 477 : libraryspace = shm_toc_lookup(toc, PARALLEL_KEY_LIBRARY, false);
1460 : 477 : StartTransactionCommand();
1461 : 477 : RestoreLibraryState(libraryspace);
1462 : 477 : CommitTransactionCommand();
1463 : :
1464 : : /* Crank up a transaction state appropriate to a parallel worker. */
1465 : 477 : tstatespace = shm_toc_lookup(toc, PARALLEL_KEY_TRANSACTION_STATE, false);
1466 : 477 : StartParallelWorkerTransaction(tstatespace);
1467 : :
1468 : : /*
1469 : : * Restore state that affects catalog access. Ideally we'd do this even
1470 : : * before calling InitPostgres, but that has order-of-initialization
1471 : : * problems, and also the relmapper would get confused during the
1472 : : * CommitTransactionCommand call above.
1473 : : */
1474 : 477 : pendingsyncsspace = shm_toc_lookup(toc, PARALLEL_KEY_PENDING_SYNCS,
1475 : : false);
1476 : 477 : RestorePendingSyncs(pendingsyncsspace);
1477 : 477 : relmapperspace = shm_toc_lookup(toc, PARALLEL_KEY_RELMAPPER_STATE, false);
1478 : 477 : RestoreRelationMap(relmapperspace);
1479 : 477 : reindexspace = shm_toc_lookup(toc, PARALLEL_KEY_REINDEX_STATE, false);
1480 : 477 : RestoreReindexState(reindexspace);
1481 : 477 : combocidspace = shm_toc_lookup(toc, PARALLEL_KEY_COMBO_CID, false);
1482 : 477 : RestoreComboCIDState(combocidspace);
1483 : :
1484 : : /* Attach to the per-session DSM segment and contained objects. */
1485 : 477 : session_dsm_handle_space =
1486 : 477 : shm_toc_lookup(toc, PARALLEL_KEY_SESSION_DSM, false);
1487 : 477 : AttachSession(*(dsm_handle *) session_dsm_handle_space);
1488 : :
1489 : : /*
1490 : : * If the transaction isolation level is REPEATABLE READ or SERIALIZABLE,
1491 : : * the leader has serialized the transaction snapshot and we must restore
1492 : : * it. At lower isolation levels, there is no transaction-lifetime
1493 : : * snapshot, but we need TransactionXmin to get set to a value which is
1494 : : * less than or equal to the xmin of every snapshot that will be used by
1495 : : * this worker. The easiest way to accomplish that is to install the
1496 : : * active snapshot as the transaction snapshot. Code running in this
1497 : : * parallel worker might take new snapshots via GetTransactionSnapshot()
1498 : : * or GetLatestSnapshot(), but it shouldn't have any way of acquiring a
1499 : : * snapshot older than the active snapshot.
1500 : : */
1501 : 477 : asnapspace = shm_toc_lookup(toc, PARALLEL_KEY_ACTIVE_SNAPSHOT, false);
1502 : 477 : tsnapspace = shm_toc_lookup(toc, PARALLEL_KEY_TRANSACTION_SNAPSHOT, true);
1503 : 477 : asnapshot = RestoreSnapshot(asnapspace);
1504 [ - + ]: 477 : tsnapshot = tsnapspace ? RestoreSnapshot(tsnapspace) : asnapshot;
1505 : 954 : RestoreTransactionSnapshot(tsnapshot,
1506 : 477 : fps->parallel_leader_pgproc);
1507 : 477 : PushActiveSnapshot(asnapshot);
1508 : :
1509 : : /*
1510 : : * We've changed which tuples we can see, and must therefore invalidate
1511 : : * system caches.
1512 : : */
1513 : 477 : InvalidateSystemCaches();
1514 : :
1515 : : /*
1516 : : * Restore GUC values from launching backend. We can't do this earlier,
1517 : : * because GUC check hooks that do catalog lookups need to see the same
1518 : : * database state as the leader. Also, the check hooks for
1519 : : * session_authorization and role assume we already set the correct role
1520 : : * OIDs.
1521 : : */
1522 : 477 : gucspace = shm_toc_lookup(toc, PARALLEL_KEY_GUC, false);
1523 : 477 : RestoreGUCState(gucspace);
1524 : :
1525 : : /*
1526 : : * Restore current user ID and security context. No verification happens
1527 : : * here, we just blindly adopt the leader's state. We can't do this till
1528 : : * after restoring GUCs, else we'll get complaints about restoring
1529 : : * session_authorization and role. (In effect, we're assuming that all
1530 : : * the restored values are okay to set, even if we are now inside a
1531 : : * restricted context.)
1532 : : */
1533 : 477 : SetUserIdAndSecContext(fps->current_user_id, fps->sec_context);
1534 : :
1535 : : /* Restore temp-namespace state to ensure search path matches leader's. */
1536 : 954 : SetTempNamespaceState(fps->temp_namespace_id,
1537 : 477 : fps->temp_toast_namespace_id);
1538 : :
1539 : : /* Restore uncommitted enums. */
1540 : 477 : uncommittedenumsspace = shm_toc_lookup(toc, PARALLEL_KEY_UNCOMMITTEDENUMS,
1541 : : false);
1542 : 477 : RestoreUncommittedEnums(uncommittedenumsspace);
1543 : :
1544 : : /* Restore the ClientConnectionInfo. */
1545 : 477 : clientconninfospace = shm_toc_lookup(toc, PARALLEL_KEY_CLIENTCONNINFO,
1546 : : false);
1547 : 477 : RestoreClientConnectionInfo(clientconninfospace);
1548 : :
1549 : : /*
1550 : : * Initialize SystemUser now that MyClientConnectionInfo is restored. Also
1551 : : * ensure that auth_method is actually valid, aka authn_id is not NULL.
1552 : : */
1553 [ + - ]: 477 : if (MyClientConnectionInfo.authn_id)
1554 : 0 : InitializeSystemUser(MyClientConnectionInfo.authn_id,
1555 : 0 : hba_authname(MyClientConnectionInfo.auth_method));
1556 : :
1557 : : /* Attach to the leader's serializable transaction, if SERIALIZABLE. */
1558 : 477 : AttachSerializableXact(fps->serializable_xact_handle);
1559 : :
1560 : : /*
1561 : : * We've initialized all of our state now; nothing should change
1562 : : * hereafter.
1563 : : */
1564 : 477 : InitializingParallelWorker = false;
1565 : 477 : EnterParallelMode();
1566 : :
1567 : : /*
1568 : : * Time to do the real work: invoke the caller-supplied code.
1569 : : */
1570 : 477 : entrypt(seg, toc);
1571 : :
1572 : : /* Must exit parallel mode to pop active snapshot. */
1573 : 477 : ExitParallelMode();
1574 : :
1575 : : /* Must pop active snapshot so snapmgr.c doesn't complain. */
1576 : 477 : PopActiveSnapshot();
1577 : :
1578 : : /* Shut down the parallel-worker transaction. */
1579 : 477 : EndParallelWorkerTransaction();
1580 : :
1581 : : /* Detach from the per-session DSM segment. */
1582 : 477 : DetachSession();
1583 : :
1584 : : /* Report success. */
1585 : 477 : pq_putmessage(PqMsg_Terminate, NULL, 0);
1586 [ - + ]: 477 : }
1587 : :
1588 : : /*
1589 : : * Update shared memory with the ending location of the last WAL record we
1590 : : * wrote, if it's greater than the value already stored there.
1591 : : */
1592 : : void
1593 : 475 : ParallelWorkerReportLastRecEnd(XLogRecPtr last_xlog_end)
1594 : : {
1595 : 475 : FixedParallelState *fps = MyFixedParallelState;
1596 : :
1597 [ + - ]: 475 : Assert(fps != NULL);
1598 [ - + ]: 475 : SpinLockAcquire(&fps->mutex);
1599 [ + + ]: 475 : if (fps->last_xlog_end < last_xlog_end)
1600 : 7 : fps->last_xlog_end = last_xlog_end;
1601 : 475 : SpinLockRelease(&fps->mutex);
1602 : 475 : }
1603 : :
1604 : : /*
1605 : : * Make sure the leader tries to read from our error queue one more time.
1606 : : * This guards against the case where we exit uncleanly without sending an
1607 : : * ErrorResponse to the leader, for example because some code calls proc_exit
1608 : : * directly.
1609 : : *
1610 : : * Also explicitly detach from dsm segment so that subsystems using
1611 : : * on_dsm_detach() have a chance to send stats before the stats subsystem is
1612 : : * shut down as part of a before_shmem_exit() hook.
1613 : : *
1614 : : * One might think this could instead be solved by carefully ordering the
1615 : : * attaching to dsm segments, so that the pgstats segments get detached from
1616 : : * later than the parallel query one. That turns out to not work because the
1617 : : * stats hash might need to grow which can cause new segments to be allocated,
1618 : : * which then will be detached from earlier.
1619 : : */
1620 : : static void
1621 : 477 : ParallelWorkerShutdown(int code, Datum arg)
1622 : : {
1623 : 954 : SendProcSignal(ParallelLeaderPid,
1624 : : PROCSIG_PARALLEL_MESSAGE,
1625 : 477 : ParallelLeaderProcNumber);
1626 : :
1627 : 477 : dsm_detach((dsm_segment *) DatumGetPointer(arg));
1628 : 477 : }
1629 : :
1630 : : /*
1631 : : * Look up (and possibly load) a parallel worker entry point function.
1632 : : *
1633 : : * For functions contained in the core code, we use library name "postgres"
1634 : : * and consult the InternalParallelWorkers array. External functions are
1635 : : * looked up, and loaded if necessary, using load_external_function().
1636 : : *
1637 : : * The point of this is to pass function names as strings across process
1638 : : * boundaries. We can't pass actual function addresses because of the
1639 : : * possibility that the function has been loaded at a different address
1640 : : * in a different process. This is obviously a hazard for functions in
1641 : : * loadable libraries, but it can happen even for functions in the core code
1642 : : * on platforms using EXEC_BACKEND (e.g., Windows).
1643 : : *
1644 : : * At some point it might be worthwhile to get rid of InternalParallelWorkers[]
1645 : : * in favor of applying load_external_function() for core functions too;
1646 : : * but that raises portability issues that are not worth addressing now.
1647 : : */
1648 : : static parallel_worker_main_type
1649 : 477 : LookupParallelWorkerFunction(const char *libraryname, const char *funcname)
1650 : : {
1651 : : /*
1652 : : * If the function is to be loaded from postgres itself, search the
1653 : : * InternalParallelWorkers array.
1654 : : */
1655 [ - + ]: 477 : if (strcmp(libraryname, "postgres") == 0)
1656 : : {
1657 : 477 : int i;
1658 : :
1659 [ + - ]: 558 : for (i = 0; i < lengthof(InternalParallelWorkers); i++)
1660 : : {
1661 [ + + ]: 558 : if (strcmp(InternalParallelWorkers[i].fn_name, funcname) == 0)
1662 : 477 : return InternalParallelWorkers[i].fn_addr;
1663 : 81 : }
1664 : :
1665 : : /* We can only reach this by programming error. */
1666 [ # # # # ]: 0 : elog(ERROR, "internal function \"%s\" not found", funcname);
1667 [ - + - ]: 477 : }
1668 : :
1669 : : /* Otherwise load from external library. */
1670 : 0 : return (parallel_worker_main_type)
1671 : 0 : load_external_function(libraryname, funcname, true, NULL);
1672 : 477 : }
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