Line data Source code
1 : /*------------------------------------------------------------------------------------
2 : *
3 : * test_custom_var_stats.c
4 : * Test module for variable-sized custom pgstats
5 : *
6 : * Copyright (c) 2025-2026, PostgreSQL Global Development Group
7 : *
8 : * IDENTIFICATION
9 : * src/test/modules/test_custom_var_stats/test_custom_var_stats.c
10 : *
11 : * ------------------------------------------------------------------------------------
12 : */
13 : #include "postgres.h"
14 :
15 : #include "common/hashfn.h"
16 : #include "funcapi.h"
17 : #include "storage/dsm_registry.h"
18 : #include "utils/builtins.h"
19 : #include "utils/pgstat_internal.h"
20 :
21 0 : PG_MODULE_MAGIC_EXT(
22 : .name = "test_custom_var_stats",
23 : .version = PG_VERSION
24 : );
25 :
26 : #define TEST_CUSTOM_VAR_MAGIC_NUMBER (0xBEEFBEEF)
27 :
28 : /*--------------------------------------------------------------------------
29 : * Macros and constants
30 : *--------------------------------------------------------------------------
31 : */
32 :
33 : /*
34 : * Kind ID for test_custom_var_stats statistics.
35 : */
36 : #define PGSTAT_KIND_TEST_CUSTOM_VAR_STATS 25
37 :
38 : /* File paths for auxiliary data serialization */
39 : #define TEST_CUSTOM_AUX_DATA_DESC "pg_stat/test_custom_var_stats_desc.stats"
40 :
41 : /*
42 : * Hash statistic name to generate entry index for pgstat lookup.
43 : */
44 : #define PGSTAT_CUSTOM_VAR_STATS_IDX(name) hash_bytes_extended((const unsigned char *) name, strlen(name), 0)
45 :
46 : /*--------------------------------------------------------------------------
47 : * Type definitions
48 : *--------------------------------------------------------------------------
49 : */
50 :
51 : /* Backend-local pending statistics before flush to shared memory */
52 : typedef struct PgStat_StatCustomVarEntry
53 : {
54 : PgStat_Counter numcalls; /* times statistic was incremented */
55 : } PgStat_StatCustomVarEntry;
56 :
57 : /* Shared memory statistics entry visible to all backends */
58 : typedef struct PgStatShared_CustomVarEntry
59 : {
60 : PgStatShared_Common header; /* standard pgstat entry header */
61 : PgStat_StatCustomVarEntry stats; /* custom statistics data */
62 : dsa_pointer description; /* pointer to description string in DSA */
63 : } PgStatShared_CustomVarEntry;
64 :
65 : /*--------------------------------------------------------------------------
66 : * Global Variables
67 : *--------------------------------------------------------------------------
68 : */
69 :
70 : /* File handle for auxiliary data serialization */
71 : static FILE *fd_description = NULL;
72 :
73 : /* Current write offset in fd_description file */
74 : static pgoff_t fd_description_offset = 0;
75 :
76 : /* DSA area for storing variable-length description strings */
77 : static dsa_area *custom_stats_description_dsa = NULL;
78 :
79 : /*--------------------------------------------------------------------------
80 : * Function prototypes
81 : *--------------------------------------------------------------------------
82 : */
83 :
84 : /* Flush callback: merge pending stats into shared memory */
85 : static bool test_custom_stats_var_flush_pending_cb(PgStat_EntryRef *entry_ref,
86 : bool nowait);
87 :
88 : /* Serialization callback: write auxiliary entry data */
89 : static void test_custom_stats_var_to_serialized_data(const PgStat_HashKey *key,
90 : const PgStatShared_Common *header,
91 : FILE *statfile);
92 :
93 : /* Deserialization callback: read auxiliary entry data */
94 : static bool test_custom_stats_var_from_serialized_data(const PgStat_HashKey *key,
95 : PgStatShared_Common *header,
96 : FILE *statfile);
97 :
98 : /* Finish callback: end of statistics file operations */
99 : static void test_custom_stats_var_finish(PgStat_StatsFileOp status);
100 :
101 : /*--------------------------------------------------------------------------
102 : * Custom kind configuration
103 : *--------------------------------------------------------------------------
104 : */
105 :
106 : static const PgStat_KindInfo custom_stats = {
107 : .name = "test_custom_var_stats",
108 : .fixed_amount = false, /* variable number of entries */
109 : .write_to_file = true, /* persist across restarts */
110 : .track_entry_count = true, /* count active entries */
111 : .accessed_across_databases = true, /* global statistics */
112 : .shared_size = sizeof(PgStatShared_CustomVarEntry),
113 : .shared_data_off = offsetof(PgStatShared_CustomVarEntry, stats),
114 : .shared_data_len = sizeof(((PgStatShared_CustomVarEntry *) 0)->stats),
115 : .pending_size = sizeof(PgStat_StatCustomVarEntry),
116 : .flush_pending_cb = test_custom_stats_var_flush_pending_cb,
117 : .to_serialized_data = test_custom_stats_var_to_serialized_data,
118 : .from_serialized_data = test_custom_stats_var_from_serialized_data,
119 : .finish = test_custom_stats_var_finish,
120 : };
121 :
122 : /*--------------------------------------------------------------------------
123 : * Module initialization
124 : *--------------------------------------------------------------------------
125 : */
126 :
127 : void
128 0 : _PG_init(void)
129 : {
130 : /* Must be loaded via shared_preload_libraries */
131 0 : if (!process_shared_preload_libraries_in_progress)
132 0 : return;
133 :
134 : /* Register custom statistics kind */
135 0 : pgstat_register_kind(PGSTAT_KIND_TEST_CUSTOM_VAR_STATS, &custom_stats);
136 0 : }
137 :
138 : /*--------------------------------------------------------------------------
139 : * Statistics callback functions
140 : *--------------------------------------------------------------------------
141 : */
142 :
143 : /*
144 : * test_custom_stats_var_flush_pending_cb
145 : * Merge pending backend statistics into shared memory
146 : *
147 : * Called by pgstat collector to flush accumulated local statistics
148 : * to shared memory where other backends can read them.
149 : *
150 : * Returns false only if nowait=true and lock acquisition fails.
151 : */
152 : static bool
153 0 : test_custom_stats_var_flush_pending_cb(PgStat_EntryRef *entry_ref, bool nowait)
154 : {
155 0 : PgStat_StatCustomVarEntry *pending_entry;
156 0 : PgStatShared_CustomVarEntry *shared_entry;
157 :
158 0 : pending_entry = (PgStat_StatCustomVarEntry *) entry_ref->pending;
159 0 : shared_entry = (PgStatShared_CustomVarEntry *) entry_ref->shared_stats;
160 :
161 0 : if (!pgstat_lock_entry(entry_ref, nowait))
162 0 : return false;
163 :
164 : /* Add pending counts to shared totals */
165 0 : shared_entry->stats.numcalls += pending_entry->numcalls;
166 :
167 0 : pgstat_unlock_entry(entry_ref);
168 :
169 0 : return true;
170 0 : }
171 :
172 : /*
173 : * test_custom_stats_var_to_serialized_data() -
174 : *
175 : * Serialize auxiliary data (descriptions) for custom statistics entries
176 : * to a secondary statistics file. This is called while writing the statistics
177 : * to disk.
178 : *
179 : * This callback writes a mix of data within the main pgstats file and a
180 : * secondary statistics file. The following data is written to the main file for
181 : * each entry:
182 : * - An arbitrary magic number.
183 : * - An offset. This is used to know the location we need to look at
184 : * to retrieve the information from the second file.
185 : *
186 : * The following data is written to the secondary statistics file:
187 : * - The entry key, cross-checked with the data from the main file
188 : * when reloaded.
189 : * - The length of the description.
190 : * - The description data itself.
191 : */
192 : static void
193 0 : test_custom_stats_var_to_serialized_data(const PgStat_HashKey *key,
194 : const PgStatShared_Common *header,
195 : FILE *statfile)
196 : {
197 0 : char *description;
198 0 : size_t len;
199 0 : const PgStatShared_CustomVarEntry *entry = (const PgStatShared_CustomVarEntry *) header;
200 0 : bool found;
201 0 : uint32 magic_number = TEST_CUSTOM_VAR_MAGIC_NUMBER;
202 :
203 : /*
204 : * First mark the main file with a magic number, keeping a trace that some
205 : * auxiliary data will exist in the secondary statistics file.
206 : */
207 0 : pgstat_write_chunk_s(statfile, &magic_number);
208 :
209 : /* Open statistics file for writing. */
210 0 : if (!fd_description)
211 : {
212 0 : fd_description = AllocateFile(TEST_CUSTOM_AUX_DATA_DESC, PG_BINARY_W);
213 0 : if (fd_description == NULL)
214 : {
215 0 : ereport(LOG,
216 : (errcode_for_file_access(),
217 : errmsg("could not open statistics file \"%s\" for writing: %m",
218 : TEST_CUSTOM_AUX_DATA_DESC)));
219 0 : return;
220 : }
221 :
222 : /* Initialize offset for secondary statistics file. */
223 0 : fd_description_offset = 0;
224 0 : }
225 :
226 : /* Write offset to the main data file */
227 0 : pgstat_write_chunk_s(statfile, &fd_description_offset);
228 :
229 : /*
230 : * First write the entry key to the secondary statistics file. This will
231 : * be cross-checked with the key read from main stats file at loading
232 : * time.
233 : */
234 0 : pgstat_write_chunk_s(fd_description, (PgStat_HashKey *) key);
235 0 : fd_description_offset += sizeof(PgStat_HashKey);
236 :
237 0 : if (!custom_stats_description_dsa)
238 0 : custom_stats_description_dsa = GetNamedDSA("test_custom_stat_dsa", &found);
239 :
240 : /* Handle entries without descriptions */
241 0 : if (!DsaPointerIsValid(entry->description) || !custom_stats_description_dsa)
242 : {
243 : /* length to description file */
244 0 : len = 0;
245 0 : pgstat_write_chunk_s(fd_description, &len);
246 0 : fd_description_offset += sizeof(size_t);
247 0 : return;
248 : }
249 :
250 : /*
251 : * Retrieve description from DSA, then write the length followed by the
252 : * description.
253 : */
254 0 : description = dsa_get_address(custom_stats_description_dsa,
255 0 : entry->description);
256 0 : len = strlen(description) + 1;
257 0 : pgstat_write_chunk_s(fd_description, &len);
258 0 : pgstat_write_chunk(fd_description, description, len);
259 :
260 : /*
261 : * Update offset for next entry, counting for the length (size_t) of the
262 : * description and the description contents.
263 : */
264 0 : fd_description_offset += len + sizeof(size_t);
265 0 : }
266 :
267 : /*
268 : * test_custom_stats_var_from_serialized_data() -
269 : *
270 : * Read auxiliary data (descriptions) for custom statistics entries from
271 : * the secondary statistics file. This is called while loading the statistics
272 : * at startup.
273 : *
274 : * See the top of test_custom_stats_var_to_serialized_data() for a
275 : * detailed description of the data layout read here.
276 : */
277 : static bool
278 0 : test_custom_stats_var_from_serialized_data(const PgStat_HashKey *key,
279 : PgStatShared_Common *header,
280 : FILE *statfile)
281 : {
282 0 : PgStatShared_CustomVarEntry *entry;
283 0 : dsa_pointer dp;
284 0 : size_t len;
285 0 : pgoff_t offset;
286 0 : char *buffer;
287 0 : bool found;
288 0 : uint32 magic_number = 0;
289 0 : PgStat_HashKey file_key;
290 :
291 : /* Check the magic number first, in the main file. */
292 0 : if (!pgstat_read_chunk_s(statfile, &magic_number))
293 : {
294 0 : elog(WARNING, "failed to read magic number from statistics file");
295 0 : return false;
296 : }
297 :
298 0 : if (magic_number != TEST_CUSTOM_VAR_MAGIC_NUMBER)
299 : {
300 0 : elog(WARNING, "found magic number %u from statistics file, should be %u",
301 : magic_number, TEST_CUSTOM_VAR_MAGIC_NUMBER);
302 0 : return false;
303 : }
304 :
305 : /*
306 : * Read the offset from the main stats file, to be able to read the
307 : * auxiliary data from the secondary statistics file.
308 : */
309 0 : if (!pgstat_read_chunk_s(statfile, &offset))
310 : {
311 0 : elog(WARNING, "failed to read metadata offset from statistics file");
312 0 : return false;
313 : }
314 :
315 : /* Open statistics file for reading if not already open */
316 0 : if (!fd_description)
317 : {
318 0 : fd_description = AllocateFile(TEST_CUSTOM_AUX_DATA_DESC, PG_BINARY_R);
319 0 : if (fd_description == NULL)
320 : {
321 0 : if (errno != ENOENT)
322 0 : ereport(LOG,
323 : (errcode_for_file_access(),
324 : errmsg("could not open statistics file \"%s\" for reading: %m",
325 : TEST_CUSTOM_AUX_DATA_DESC)));
326 0 : pgstat_reset_of_kind(PGSTAT_KIND_TEST_CUSTOM_VAR_STATS);
327 0 : return false;
328 : }
329 0 : }
330 :
331 : /* Read data from the secondary statistics file, at the specified offset */
332 0 : if (fseeko(fd_description, offset, SEEK_SET) != 0)
333 : {
334 0 : elog(WARNING, "could not seek in file \"%s\": %m",
335 : TEST_CUSTOM_AUX_DATA_DESC);
336 0 : return false;
337 : }
338 :
339 : /* Read the hash key from the secondary statistics file */
340 0 : if (!pgstat_read_chunk_s(fd_description, &file_key))
341 : {
342 0 : elog(WARNING, "failed to read hash key from file");
343 0 : return false;
344 : }
345 :
346 : /* Check key consistency */
347 0 : if (file_key.kind != key->kind ||
348 0 : file_key.dboid != key->dboid ||
349 0 : file_key.objid != key->objid)
350 : {
351 0 : elog(WARNING, "found entry key %u/%u/%" PRIu64 " not matching with %u/%u/%" PRIu64,
352 : file_key.kind, file_key.dboid, file_key.objid,
353 : key->kind, key->dboid, key->objid);
354 0 : return false;
355 : }
356 :
357 0 : entry = (PgStatShared_CustomVarEntry *) header;
358 :
359 : /* Read the description length and its data */
360 0 : if (!pgstat_read_chunk_s(fd_description, &len))
361 : {
362 0 : elog(WARNING, "failed to read metadata length from statistics file");
363 0 : return false;
364 : }
365 :
366 : /* Handle empty descriptions */
367 0 : if (len == 0)
368 : {
369 0 : entry->description = InvalidDsaPointer;
370 0 : return true;
371 : }
372 :
373 : /* Initialize DSA if needed */
374 0 : if (!custom_stats_description_dsa)
375 0 : custom_stats_description_dsa = GetNamedDSA("test_custom_stat_dsa", &found);
376 :
377 0 : if (!custom_stats_description_dsa)
378 : {
379 0 : elog(WARNING, "could not access DSA for custom statistics descriptions");
380 0 : return false;
381 : }
382 :
383 0 : buffer = palloc(len);
384 0 : if (!pgstat_read_chunk(fd_description, buffer, len))
385 : {
386 0 : pfree(buffer);
387 0 : elog(WARNING, "failed to read description from file");
388 0 : return false;
389 : }
390 :
391 : /* Allocate space in DSA and copy the description */
392 0 : dp = dsa_allocate(custom_stats_description_dsa, len);
393 0 : memcpy(dsa_get_address(custom_stats_description_dsa, dp), buffer, len);
394 0 : entry->description = dp;
395 0 : pfree(buffer);
396 :
397 0 : return true;
398 0 : }
399 :
400 : /*
401 : * test_custom_stats_var_finish() -
402 : *
403 : * Cleanup function called at the end of statistics file operations.
404 : * Handles closing files and cleanup based on the operation type.
405 : */
406 : static void
407 0 : test_custom_stats_var_finish(PgStat_StatsFileOp status)
408 : {
409 0 : switch (status)
410 : {
411 : case STATS_WRITE:
412 0 : if (!fd_description)
413 0 : return;
414 :
415 0 : fd_description_offset = 0;
416 :
417 : /* Check for write errors and cleanup if necessary */
418 0 : if (ferror(fd_description))
419 : {
420 0 : ereport(LOG,
421 : (errcode_for_file_access(),
422 : errmsg("could not write to file \"%s\": %m",
423 : TEST_CUSTOM_AUX_DATA_DESC)));
424 0 : FreeFile(fd_description);
425 0 : unlink(TEST_CUSTOM_AUX_DATA_DESC);
426 0 : }
427 0 : else if (FreeFile(fd_description) < 0)
428 : {
429 0 : ereport(LOG,
430 : (errcode_for_file_access(),
431 : errmsg("could not close file \"%s\": %m",
432 : TEST_CUSTOM_AUX_DATA_DESC)));
433 0 : unlink(TEST_CUSTOM_AUX_DATA_DESC);
434 0 : }
435 0 : break;
436 :
437 : case STATS_READ:
438 0 : if (fd_description)
439 0 : FreeFile(fd_description);
440 :
441 : /* Remove the file after reading */
442 0 : elog(DEBUG2, "removing file \"%s\"", TEST_CUSTOM_AUX_DATA_DESC);
443 0 : unlink(TEST_CUSTOM_AUX_DATA_DESC);
444 0 : break;
445 :
446 : case STATS_DISCARD:
447 : {
448 0 : int ret;
449 :
450 : /* Attempt to remove the file */
451 0 : ret = unlink(TEST_CUSTOM_AUX_DATA_DESC);
452 0 : if (ret != 0)
453 : {
454 0 : if (errno == ENOENT)
455 0 : elog(LOG,
456 : "didn't need to unlink file \"%s\" - didn't exist",
457 : TEST_CUSTOM_AUX_DATA_DESC);
458 : else
459 0 : ereport(LOG,
460 : (errcode_for_file_access(),
461 : errmsg("could not unlink file \"%s\": %m",
462 : TEST_CUSTOM_AUX_DATA_DESC)));
463 0 : }
464 : else
465 : {
466 0 : ereport(LOG,
467 : (errmsg_internal("unlinked file \"%s\"",
468 : TEST_CUSTOM_AUX_DATA_DESC)));
469 : }
470 0 : }
471 0 : break;
472 : }
473 :
474 0 : fd_description = NULL;
475 0 : }
476 :
477 : /*--------------------------------------------------------------------------
478 : * Helper functions
479 : *--------------------------------------------------------------------------
480 : */
481 :
482 : /*
483 : * test_custom_stats_var_fetch_entry
484 : * Look up custom statistic by name
485 : *
486 : * Returns statistics entry from shared memory, or NULL if not found.
487 : */
488 : static PgStat_StatCustomVarEntry *
489 0 : test_custom_stats_var_fetch_entry(const char *stat_name)
490 : {
491 : /* Fetch entry by hashed name */
492 0 : return (PgStat_StatCustomVarEntry *)
493 0 : pgstat_fetch_entry(PGSTAT_KIND_TEST_CUSTOM_VAR_STATS,
494 : InvalidOid,
495 0 : PGSTAT_CUSTOM_VAR_STATS_IDX(stat_name));
496 : }
497 :
498 : /*--------------------------------------------------------------------------
499 : * SQL-callable functions
500 : *--------------------------------------------------------------------------
501 : */
502 :
503 : /*
504 : * test_custom_stats_var_create
505 : * Create new custom statistic entry
506 : *
507 : * Initializes a statistics entry with the given name and description.
508 : */
509 0 : PG_FUNCTION_INFO_V1(test_custom_stats_var_create);
510 : Datum
511 0 : test_custom_stats_var_create(PG_FUNCTION_ARGS)
512 : {
513 0 : PgStat_EntryRef *entry_ref;
514 0 : PgStatShared_CustomVarEntry *shared_entry;
515 0 : char *stat_name = text_to_cstring(PG_GETARG_TEXT_PP(0));
516 0 : char *description = text_to_cstring(PG_GETARG_TEXT_PP(1));
517 0 : dsa_pointer dp = InvalidDsaPointer;
518 0 : bool found;
519 :
520 : /* Validate name length first */
521 0 : if (strlen(stat_name) >= NAMEDATALEN)
522 0 : ereport(ERROR,
523 : (errcode(ERRCODE_NAME_TOO_LONG),
524 : errmsg("custom statistic name \"%s\" is too long", stat_name),
525 : errdetail("Name must be less than %d characters.", NAMEDATALEN)));
526 :
527 : /* Initialize DSA and description provided */
528 0 : if (!custom_stats_description_dsa)
529 0 : custom_stats_description_dsa = GetNamedDSA("test_custom_stat_dsa", &found);
530 :
531 0 : if (!custom_stats_description_dsa)
532 0 : ereport(ERROR,
533 : (errmsg("could not access DSA for custom statistics descriptions")));
534 :
535 : /* Allocate space in DSA and copy description */
536 0 : dp = dsa_allocate(custom_stats_description_dsa, strlen(description) + 1);
537 0 : memcpy(dsa_get_address(custom_stats_description_dsa, dp),
538 : description,
539 : strlen(description) + 1);
540 :
541 : /* Create or get existing entry */
542 0 : entry_ref = pgstat_get_entry_ref_locked(PGSTAT_KIND_TEST_CUSTOM_VAR_STATS, InvalidOid,
543 0 : PGSTAT_CUSTOM_VAR_STATS_IDX(stat_name), true);
544 :
545 0 : if (!entry_ref)
546 0 : PG_RETURN_VOID();
547 :
548 0 : shared_entry = (PgStatShared_CustomVarEntry *) entry_ref->shared_stats;
549 :
550 : /* Zero-initialize statistics */
551 0 : memset(&shared_entry->stats, 0, sizeof(shared_entry->stats));
552 :
553 : /* Store description pointer */
554 0 : shared_entry->description = dp;
555 :
556 0 : pgstat_unlock_entry(entry_ref);
557 :
558 0 : PG_RETURN_VOID();
559 0 : }
560 :
561 : /*
562 : * test_custom_stats_var_update
563 : * Increment custom statistic counter
564 : *
565 : * Increments call count in backend-local memory. Changes are flushed
566 : * to shared memory by the statistics collector.
567 : */
568 0 : PG_FUNCTION_INFO_V1(test_custom_stats_var_update);
569 : Datum
570 0 : test_custom_stats_var_update(PG_FUNCTION_ARGS)
571 : {
572 0 : char *stat_name = text_to_cstring(PG_GETARG_TEXT_PP(0));
573 0 : PgStat_EntryRef *entry_ref;
574 0 : PgStat_StatCustomVarEntry *pending_entry;
575 :
576 : /* Get pending entry in local memory */
577 0 : entry_ref = pgstat_prep_pending_entry(PGSTAT_KIND_TEST_CUSTOM_VAR_STATS, InvalidOid,
578 0 : PGSTAT_CUSTOM_VAR_STATS_IDX(stat_name), NULL);
579 :
580 0 : pending_entry = (PgStat_StatCustomVarEntry *) entry_ref->pending;
581 0 : pending_entry->numcalls++;
582 :
583 0 : PG_RETURN_VOID();
584 0 : }
585 :
586 : /*
587 : * test_custom_stats_var_drop
588 : * Remove custom statistic entry
589 : *
590 : * Drops the named statistic from shared memory.
591 : */
592 0 : PG_FUNCTION_INFO_V1(test_custom_stats_var_drop);
593 : Datum
594 0 : test_custom_stats_var_drop(PG_FUNCTION_ARGS)
595 : {
596 0 : char *stat_name = text_to_cstring(PG_GETARG_TEXT_PP(0));
597 :
598 : /* Drop entry and request GC if the entry could not be freed */
599 0 : if (!pgstat_drop_entry(PGSTAT_KIND_TEST_CUSTOM_VAR_STATS, InvalidOid,
600 0 : PGSTAT_CUSTOM_VAR_STATS_IDX(stat_name)))
601 0 : pgstat_request_entry_refs_gc();
602 :
603 0 : PG_RETURN_VOID();
604 0 : }
605 :
606 : /*
607 : * test_custom_stats_var_report
608 : * Retrieve custom statistic values
609 : *
610 : * Returns single row with statistic name, call count, and description if the
611 : * statistic exists, otherwise returns no rows.
612 : */
613 0 : PG_FUNCTION_INFO_V1(test_custom_stats_var_report);
614 : Datum
615 0 : test_custom_stats_var_report(PG_FUNCTION_ARGS)
616 : {
617 0 : FuncCallContext *funcctx;
618 0 : char *stat_name;
619 0 : PgStat_StatCustomVarEntry *stat_entry;
620 :
621 0 : if (SRF_IS_FIRSTCALL())
622 : {
623 0 : TupleDesc tupdesc;
624 0 : MemoryContext oldcontext;
625 :
626 : /* Initialize SRF context */
627 0 : funcctx = SRF_FIRSTCALL_INIT();
628 0 : oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
629 :
630 : /* Get composite return type */
631 0 : if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
632 0 : elog(ERROR, "test_custom_stats_var_report: return type is not composite");
633 :
634 0 : funcctx->tuple_desc = BlessTupleDesc(tupdesc);
635 0 : funcctx->max_calls = 1; /* single row result */
636 :
637 0 : MemoryContextSwitchTo(oldcontext);
638 0 : }
639 :
640 0 : funcctx = SRF_PERCALL_SETUP();
641 :
642 0 : if (funcctx->call_cntr < funcctx->max_calls)
643 : {
644 0 : Datum values[3];
645 0 : bool nulls[3] = {false, false, false};
646 0 : HeapTuple tuple;
647 0 : PgStat_EntryRef *entry_ref;
648 0 : PgStatShared_CustomVarEntry *shared_entry;
649 0 : char *description = NULL;
650 0 : bool found;
651 :
652 0 : stat_name = text_to_cstring(PG_GETARG_TEXT_PP(0));
653 0 : stat_entry = test_custom_stats_var_fetch_entry(stat_name);
654 :
655 : /* Return row only if entry exists */
656 0 : if (stat_entry)
657 : {
658 : /* Get entry ref to access shared entry */
659 0 : entry_ref = pgstat_get_entry_ref(PGSTAT_KIND_TEST_CUSTOM_VAR_STATS, InvalidOid,
660 0 : PGSTAT_CUSTOM_VAR_STATS_IDX(stat_name), false, NULL);
661 :
662 0 : if (entry_ref)
663 : {
664 0 : shared_entry = (PgStatShared_CustomVarEntry *) entry_ref->shared_stats;
665 :
666 : /* Get description from DSA if available */
667 0 : if (DsaPointerIsValid(shared_entry->description))
668 : {
669 0 : if (!custom_stats_description_dsa)
670 0 : custom_stats_description_dsa = GetNamedDSA("test_custom_stat_dsa", &found);
671 :
672 0 : if (custom_stats_description_dsa)
673 0 : description = dsa_get_address(custom_stats_description_dsa, shared_entry->description);
674 0 : }
675 0 : }
676 :
677 0 : values[0] = PointerGetDatum(cstring_to_text(stat_name));
678 0 : values[1] = Int64GetDatum(stat_entry->numcalls);
679 :
680 0 : if (description)
681 0 : values[2] = PointerGetDatum(cstring_to_text(description));
682 : else
683 0 : nulls[2] = true;
684 :
685 0 : tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
686 0 : SRF_RETURN_NEXT(funcctx, HeapTupleGetDatum(tuple));
687 0 : }
688 0 : }
689 :
690 0 : SRF_RETURN_DONE(funcctx);
691 0 : }
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