From f4ea30ca38e7fc5ba22e092a27341077b6f0dcc0 Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Tue, 24 Feb 2026 15:45:51 +0200 Subject: [PATCH v2 3/4] Convert pg_stat_statements to use the new interface --- .../pg_stat_statements/pg_stat_statements.c | 135 ++++++++---------- 1 file changed, 62 insertions(+), 73 deletions(-) diff --git a/contrib/pg_stat_statements/pg_stat_statements.c b/contrib/pg_stat_statements/pg_stat_statements.c index 4a427533bd8..a8c7f7b2441 100644 --- a/contrib/pg_stat_statements/pg_stat_statements.c +++ b/contrib/pg_stat_statements/pg_stat_statements.c @@ -258,6 +258,29 @@ typedef struct pgssSharedState pgssGlobalStats stats; /* global statistics for pgss */ } pgssSharedState; +/* Links to shared memory state */ +static pgssSharedState *pgss; +static HTAB *pgss_hash; + +static void pgss_shmem_init(void *arg); + +static ShmemStructDesc pgssSharedStateShmemDesc = +{ + .name = "pg_stat_statements", + .size = sizeof(pgssSharedState), + .init_fn = pgss_shmem_init, + .ptr = (void *) &pgss, +}; + +static ShmemHashDesc pgssSharedHashDesc = +{ + .name = "pg_stat_statements hash", + .init_size = 0, /* set from 'pgss_max' */ + .max_size = 0, /* set from 'pgss_max' */ + .ptr = &pgss_hash, +}; + + /*---- Local variables ----*/ /* Current nesting depth of planner/ExecutorRun/ProcessUtility calls */ @@ -274,10 +297,6 @@ static ExecutorFinish_hook_type prev_ExecutorFinish = NULL; static ExecutorEnd_hook_type prev_ExecutorEnd = NULL; static ProcessUtility_hook_type prev_ProcessUtility = NULL; -/* Links to shared memory state */ -static pgssSharedState *pgss = NULL; -static HTAB *pgss_hash = NULL; - /*---- GUC variables ----*/ typedef enum @@ -365,7 +384,6 @@ static void pgss_store(const char *query, int64 queryId, static void pg_stat_statements_internal(FunctionCallInfo fcinfo, pgssVersion api_version, bool showtext); -static Size pgss_memsize(void); static pgssEntry *entry_alloc(pgssHashKey *key, Size query_offset, int query_len, int encoding, bool sticky); static void entry_dealloc(void); @@ -390,6 +408,8 @@ static int comp_location(const void *a, const void *b); void _PG_init(void) { + HASHCTL info; + /* * In order to create our shared memory area, we have to be loaded via * shared_preload_libraries. If not, fall out without hooking into any of @@ -470,6 +490,19 @@ _PG_init(void) MarkGUCPrefixReserved("pg_stat_statements"); + /* + * Register our shared memory needs, including hash table + */ + ShmemRegisterStruct(&pgssSharedStateShmemDesc); + + info.keysize = sizeof(pgssHashKey); + info.entrysize = sizeof(pgssEntry); + pgssSharedHashDesc.init_size = pgss_max; + pgssSharedHashDesc.max_size = pgss_max; + ShmemRegisterHash(&pgssSharedHashDesc, + &info, + HASH_ELEM | HASH_BLOBS); + /* * Install hooks. */ @@ -494,8 +527,8 @@ _PG_init(void) } /* - * shmem_request hook: request additional shared resources. We'll allocate or - * attach to the shared resources in pgss_shmem_startup(). + * shmem_request hook: request additional shared resources. We'll initialize + * other resources in pgss_shmem_startup(). */ static void pgss_shmem_request(void) @@ -503,21 +536,31 @@ pgss_shmem_request(void) if (prev_shmem_request_hook) prev_shmem_request_hook(); - RequestAddinShmemSpace(pgss_memsize()); RequestNamedLWLockTranche("pg_stat_statements", 1); } +static void +pgss_shmem_init(void *arg) +{ + pgss->lock = &(GetNamedLWLockTranche("pg_stat_statements"))->lock; + pgss->cur_median_usage = ASSUMED_MEDIAN_INIT; + pgss->mean_query_len = ASSUMED_LENGTH_INIT; + SpinLockInit(&pgss->mutex); + pgss->extent = 0; + pgss->n_writers = 0; + pgss->gc_count = 0; + pgss->stats.dealloc = 0; + pgss->stats.stats_reset = GetCurrentTimestamp(); +} + /* - * shmem_startup hook: allocate or attach to shared memory, - * then load any pre-existing statistics from file. - * Also create and load the query-texts file, which is expected to exist - * (even if empty) while the module is enabled. + * shmem_startup hook: Load any pre-existing statistics from file at + * postmaster startup. Also create and load the query-texts file, which is + * expected to exist (even if empty) while the module is enabled. */ static void pgss_shmem_startup(void) { - bool found; - HASHCTL info; FILE *file = NULL; FILE *qfile = NULL; uint32 header; @@ -530,54 +573,14 @@ pgss_shmem_startup(void) if (prev_shmem_startup_hook) prev_shmem_startup_hook(); - /* reset in case this is a restart within the postmaster */ - pgss = NULL; - pgss_hash = NULL; - - /* - * Create or attach to the shared memory state, including hash table - */ - LWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE); - - pgss = ShmemInitStruct("pg_stat_statements", - sizeof(pgssSharedState), - &found); - - if (!found) - { - /* First time through ... */ - pgss->lock = &(GetNamedLWLockTranche("pg_stat_statements"))->lock; - pgss->cur_median_usage = ASSUMED_MEDIAN_INIT; - pgss->mean_query_len = ASSUMED_LENGTH_INIT; - SpinLockInit(&pgss->mutex); - pgss->extent = 0; - pgss->n_writers = 0; - pgss->gc_count = 0; - pgss->stats.dealloc = 0; - pgss->stats.stats_reset = GetCurrentTimestamp(); - } - - info.keysize = sizeof(pgssHashKey); - info.entrysize = sizeof(pgssEntry); - pgss_hash = ShmemInitHash("pg_stat_statements hash", - pgss_max, pgss_max, - &info, - HASH_ELEM | HASH_BLOBS); - - LWLockRelease(AddinShmemInitLock); + if (IsUnderPostmaster) + return; /* nothing to do in backends */ /* - * If we're in the postmaster (or a standalone backend...), set up a shmem - * exit hook to dump the statistics to disk. + * Set up a shmem exit hook to dump the statistics to disk on postmaster + * (or standalone backend) exit. */ - if (!IsUnderPostmaster) - on_shmem_exit(pgss_shmem_shutdown, (Datum) 0); - - /* - * Done if some other process already completed our initialization. - */ - if (found) - return; + on_shmem_exit(pgss_shmem_shutdown, (Datum) 0); /* * Note: we don't bother with locks here, because there should be no other @@ -2082,20 +2085,6 @@ pg_stat_statements_info(PG_FUNCTION_ARGS) PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls))); } -/* - * Estimate shared memory space needed. - */ -static Size -pgss_memsize(void) -{ - Size size; - - size = MAXALIGN(sizeof(pgssSharedState)); - size = add_size(size, hash_estimate_size(pgss_max, sizeof(pgssEntry))); - - return size; -} - /* * Allocate a new hashtable entry. * caller must hold an exclusive lock on pgss->lock -- 2.47.3