From: Michael Paquier Date: Sun, 4 Aug 2024 10:41:24 +0000 (+0900) Subject: Introduce pluggable APIs for Cumulative Statistics X-Git-Tag: REL_18_BETA1~2213 X-Git-Url: http://git.postgresql.org/gitweb/?a=commitdiff_plain;h=7949d9594582ab49dee221e1db1aa5401ace49d4;p=postgresql.git Introduce pluggable APIs for Cumulative Statistics This commit adds support in the backend for $subject, allowing out-of-core extensions to plug their own custom kinds of cumulative statistics. This feature has come up a few times into the lists, and the first, original, suggestion came from Andres Freund, about pg_stat_statements to use the cumulative statistics APIs in shared memory rather than its own less efficient internals. The advantage of this implementation is that this can be extended to any kind of statistics. The stats kinds are divided into two parts: - The in-core "builtin" stats kinds, with designated initializers, able to use IDs up to 128. - The "custom" stats kinds, able to use a range of IDs from 128 to 256 (128 slots available as of this patch), with information saved in TopMemoryContext. This can be made larger, if necessary. There are two types of cumulative statistics in the backend: - For fixed-numbered objects (like WAL, archiver, etc.). These are attached to the snapshot and pgstats shmem control structures for efficiency, and built-in stats kinds still do that to avoid any redirection penalty. The data of custom kinds is stored in a first array in snapshot structure and a second array in the shmem control structure, both indexed by their ID, acting as an equivalent of the builtin stats. - For variable-numbered objects (like tables, functions, etc.). These are stored in a dshash using the stats kind ID in the hash lookup key. Internally, the handling of the builtin stats is unchanged, and both fixed and variabled-numbered objects are supported. Structure definitions for builtin stats kinds are renamed to reflect better the differences with custom kinds. Like custom RMGRs, custom cumulative statistics can only be loaded with shared_preload_libraries at startup, and must allocate a unique ID shared across all the PostgreSQL extension ecosystem with the following wiki page to avoid conflicts: https://wiki.postgresql.org/wiki/CustomCumulativeStats This makes the detection of the stats kinds and their handling when reading and writing stats much easier than, say, allocating IDs for stats kinds from a shared memory counter, that may change the ID used by a stats kind across restarts. When under development, extensions can use PGSTAT_KIND_EXPERIMENTAL. Two examples that can be used as templates for fixed-numbered and variable-numbered stats kinds will be added in some follow-up commits, with tests to provide coverage. Some documentation is added to explain how to use this plugin facility. Author: Michael Paquier Reviewed-by: Dmitry Dolgov, Bertrand Drouvot Discussion: https://postgr.es/m/Zmqm9j5EO0I4W8dx@paquier.xyz --- diff --git a/doc/src/sgml/xfunc.sgml b/doc/src/sgml/xfunc.sgml index bf76490cbc0..6b029a5a35f 100644 --- a/doc/src/sgml/xfunc.sgml +++ b/doc/src/sgml/xfunc.sgml @@ -3864,6 +3864,63 @@ extern bool InjectionPointDetach(const char *name); + + Custom Cumulative Statistics + + + Is is possible for add-ins written in C-language to use custom types + of cumulative statistics registered in the + Cumulative Statistics System. + + + + First, define a PgStat_KindInfo that includes all + the information related to the custom type registered. For example: + +static const PgStat_KindInfo custom_stats = { + .name = "custom_stats", + .fixed_amount = false, + .shared_size = sizeof(PgStatShared_Custom), + .shared_data_off = offsetof(PgStatShared_Custom, stats), + .shared_data_len = sizeof(((PgStatShared_Custom *) 0)->stats), + .pending_size = sizeof(PgStat_StatCustomEntry), +} + + + Then, each backend that needs to use this custom type needs to register + it with pgstat_register_kind and a unique ID used to + store the entries related to this type of statistics: + +extern PgStat_Kind pgstat_add_kind(PgStat_Kind kind, + const PgStat_KindInfo *kind_info); + + While developing a new extension, use + PGSTAT_KIND_EXPERIMENTAL for + kind. When you are ready to release the extension + to users, reserve a kind ID at the + + Custom Cumulative Statistics page. + + + + The details of the API for PgStat_KindInfo can + be found in src/include/utils/pgstat_internal.h. + + + + The type of statistics registered is associated with a name and a unique + ID shared across the server in shared memory. Each backend using a + custom type of statistics maintains a local cache storing the information + of each custom PgStat_KindInfo. + + + + Place the extension module implementing the custom cumulative statistics + type in so that it will + be loaded early during PostgreSQL startup. + + + Using C++ for Extensibility diff --git a/src/backend/utils/activity/pgstat.c b/src/backend/utils/activity/pgstat.c index 2e13670fc1f..b2ca3f39b7a 100644 --- a/src/backend/utils/activity/pgstat.c +++ b/src/backend/utils/activity/pgstat.c @@ -49,8 +49,16 @@ * pgStatPending list. Pending statistics updates are flushed out by * pgstat_report_stat(). * + * It is possible for external modules to define custom statistics kinds, + * that can use the same properties as any built-in stats kinds. Each custom + * stats kind needs to assign a unique ID to ensure that it does not overlap + * with other extensions. In order to reserve a unique stats kind ID, refer + * to https://wiki.postgresql.org/wiki/CustomCumulativeStats. + * * The behavior of different kinds of statistics is determined by the kind's - * entry in pgstat_kind_infos, see PgStat_KindInfo for details. + * entry in pgstat_kind_builtin_infos for all the built-in statistics kinds + * defined, and pgstat_kind_custom_infos for custom kinds registered at + * startup by pgstat_register_kind(). See PgStat_KindInfo for details. * * The consistency of read accesses to statistics can be configured using the * stats_fetch_consistency GUC (see config.sgml and monitoring.sgml for the @@ -175,6 +183,8 @@ typedef struct PgStat_SnapshotEntry static void pgstat_write_statsfile(XLogRecPtr redo); static void pgstat_read_statsfile(XLogRecPtr redo); +static void pgstat_init_snapshot_fixed(void); + static void pgstat_reset_after_failure(void); static bool pgstat_flush_pending_entries(bool nowait); @@ -252,7 +262,7 @@ static bool pgstat_is_shutdown = false; /* - * The different kinds of statistics. + * The different kinds of built-in statistics. * * If reasonably possible, handling specific to one kind of stats should go * through this abstraction, rather than making more of pgstat.c aware. @@ -264,7 +274,7 @@ static bool pgstat_is_shutdown = false; * seem to be a great way of doing that, given the split across multiple * files. */ -static const PgStat_KindInfo pgstat_kind_infos[PGSTAT_NUM_KINDS] = { +static const PgStat_KindInfo pgstat_kind_builtin_infos[PGSTAT_KIND_BUILTIN_SIZE] = { /* stats kinds for variable-numbered objects */ @@ -437,6 +447,15 @@ static const PgStat_KindInfo pgstat_kind_infos[PGSTAT_NUM_KINDS] = { }, }; +/* + * Information about custom statistics kinds. + * + * These are saved in a different array than the built-in kinds to save + * in clarity with the initializations. + * + * Indexed by PGSTAT_KIND_CUSTOM_MIN, of size PGSTAT_KIND_CUSTOM_SIZE. + */ +static const PgStat_KindInfo **pgstat_kind_custom_infos = NULL; /* ------------------------------------------------------------ * Functions managing the state of the stats system for all backends. @@ -587,6 +606,8 @@ pgstat_initialize(void) pgstat_init_wal(); + pgstat_init_snapshot_fixed(); + /* Set up a process-exit hook to clean up */ before_shmem_exit(pgstat_shutdown_hook, 0); @@ -830,6 +851,8 @@ pgstat_clear_snapshot(void) memset(&pgStatLocal.snapshot.fixed_valid, 0, sizeof(pgStatLocal.snapshot.fixed_valid)); + memset(&pgStatLocal.snapshot.custom_valid, 0, + sizeof(pgStatLocal.snapshot.custom_valid)); pgStatLocal.snapshot.stats = NULL; pgStatLocal.snapshot.mode = PGSTAT_FETCH_CONSISTENCY_NONE; @@ -993,7 +1016,29 @@ pgstat_snapshot_fixed(PgStat_Kind kind) else pgstat_build_snapshot_fixed(kind); - Assert(pgStatLocal.snapshot.fixed_valid[kind]); + if (pgstat_is_kind_builtin(kind)) + Assert(pgStatLocal.snapshot.fixed_valid[kind]); + else if (pgstat_is_kind_custom(kind)) + Assert(pgStatLocal.snapshot.custom_valid[kind - PGSTAT_KIND_CUSTOM_MIN]); +} + +static void +pgstat_init_snapshot_fixed(void) +{ + /* + * Initialize fixed-numbered statistics data in snapshots, only for custom + * stats kinds. + */ + for (PgStat_Kind kind = PGSTAT_KIND_CUSTOM_MIN; kind <= PGSTAT_KIND_CUSTOM_MAX; kind++) + { + const PgStat_KindInfo *kind_info = pgstat_get_kind_info(kind); + + if (!kind_info || !kind_info->fixed_amount) + continue; + + pgStatLocal.snapshot.custom_data[kind - PGSTAT_KIND_CUSTOM_MIN] = + MemoryContextAlloc(TopMemoryContext, kind_info->shared_data_len); + } } static void @@ -1089,10 +1134,12 @@ pgstat_build_snapshot(void) /* * Build snapshot of all fixed-numbered stats. */ - for (PgStat_Kind kind = PGSTAT_KIND_FIRST_VALID; kind <= PGSTAT_KIND_LAST; kind++) + for (PgStat_Kind kind = PGSTAT_KIND_MIN; kind <= PGSTAT_KIND_MAX; kind++) { const PgStat_KindInfo *kind_info = pgstat_get_kind_info(kind); + if (!kind_info) + continue; if (!kind_info->fixed_amount) { Assert(kind_info->snapshot_cb == NULL); @@ -1109,6 +1156,20 @@ static void pgstat_build_snapshot_fixed(PgStat_Kind kind) { const PgStat_KindInfo *kind_info = pgstat_get_kind_info(kind); + int idx; + bool *valid; + + /* Position in fixed_valid or custom_valid */ + if (pgstat_is_kind_builtin(kind)) + { + idx = kind; + valid = pgStatLocal.snapshot.fixed_valid; + } + else + { + idx = kind - PGSTAT_KIND_CUSTOM_MIN; + valid = pgStatLocal.snapshot.custom_valid; + } Assert(kind_info->fixed_amount); Assert(kind_info->snapshot_cb != NULL); @@ -1116,21 +1177,21 @@ pgstat_build_snapshot_fixed(PgStat_Kind kind) if (pgstat_fetch_consistency == PGSTAT_FETCH_CONSISTENCY_NONE) { /* rebuild every time */ - pgStatLocal.snapshot.fixed_valid[kind] = false; + valid[idx] = false; } - else if (pgStatLocal.snapshot.fixed_valid[kind]) + else if (valid[idx]) { /* in snapshot mode we shouldn't get called again */ Assert(pgstat_fetch_consistency == PGSTAT_FETCH_CONSISTENCY_CACHE); return; } - Assert(!pgStatLocal.snapshot.fixed_valid[kind]); + Assert(!valid[idx]); kind_info->snapshot_cb(); - Assert(!pgStatLocal.snapshot.fixed_valid[kind]); - pgStatLocal.snapshot.fixed_valid[kind] = true; + Assert(!valid[idx]); + valid[idx] = true; } @@ -1286,30 +1347,131 @@ pgstat_flush_pending_entries(bool nowait) PgStat_Kind pgstat_get_kind_from_str(char *kind_str) { - for (PgStat_Kind kind = PGSTAT_KIND_FIRST_VALID; kind <= PGSTAT_KIND_LAST; kind++) + for (PgStat_Kind kind = PGSTAT_KIND_BUILTIN_MIN; kind <= PGSTAT_KIND_BUILTIN_MAX; kind++) { - if (pg_strcasecmp(kind_str, pgstat_kind_infos[kind].name) == 0) + if (pg_strcasecmp(kind_str, pgstat_kind_builtin_infos[kind].name) == 0) return kind; } + /* Check the custom set of cumulative stats */ + if (pgstat_kind_custom_infos) + { + for (PgStat_Kind kind = PGSTAT_KIND_CUSTOM_MIN; kind <= PGSTAT_KIND_CUSTOM_MAX; kind++) + { + uint32 idx = kind - PGSTAT_KIND_CUSTOM_MIN; + + if (pgstat_kind_custom_infos[idx] && + pg_strcasecmp(kind_str, pgstat_kind_custom_infos[idx]->name) == 0) + return kind; + } + } + ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE), errmsg("invalid statistics kind: \"%s\"", kind_str))); - return PGSTAT_KIND_DATABASE; /* avoid compiler warnings */ + return PGSTAT_KIND_INVALID; /* avoid compiler warnings */ } static inline bool pgstat_is_kind_valid(PgStat_Kind kind) { - return kind >= PGSTAT_KIND_FIRST_VALID && kind <= PGSTAT_KIND_LAST; + return pgstat_is_kind_builtin(kind) || pgstat_is_kind_custom(kind); } const PgStat_KindInfo * pgstat_get_kind_info(PgStat_Kind kind) { - Assert(pgstat_is_kind_valid(kind)); + if (pgstat_is_kind_builtin(kind)) + return &pgstat_kind_builtin_infos[kind]; + + if (pgstat_is_kind_custom(kind)) + { + uint32 idx = kind - PGSTAT_KIND_CUSTOM_MIN; - return &pgstat_kind_infos[kind]; + if (pgstat_kind_custom_infos == NULL || + pgstat_kind_custom_infos[idx] == NULL) + return NULL; + return pgstat_kind_custom_infos[idx]; + } + + return NULL; +} + +/* + * Register a new stats kind. + * + * PgStat_Kinds must be globally unique across all extensions. Refer + * to https://wiki.postgresql.org/wiki/CustomCumulativeStats to reserve a + * unique ID for your extension, to avoid conflicts with other extension + * developers. During development, use PGSTAT_KIND_EXPERIMENTAL to avoid + * needlessly reserving a new ID. + */ +void +pgstat_register_kind(PgStat_Kind kind, const PgStat_KindInfo *kind_info) +{ + uint32 idx = kind - PGSTAT_KIND_CUSTOM_MIN; + + if (kind_info->name == NULL || strlen(kind_info->name) == 0) + ereport(ERROR, + (errmsg("custom cumulative statistics name is invalid"), + errhint("Provide a non-empty name for the custom cumulative statistics."))); + + if (!pgstat_is_kind_custom(kind)) + ereport(ERROR, (errmsg("custom cumulative statistics ID %u is out of range", kind), + errhint("Provide a custom cumulative statistics ID between %u and %u.", + PGSTAT_KIND_CUSTOM_MIN, PGSTAT_KIND_CUSTOM_MAX))); + + if (!process_shared_preload_libraries_in_progress) + ereport(ERROR, + (errmsg("failed to register custom cumulative statistics \"%s\" with ID %u", kind_info->name, kind), + errdetail("Custom cumulative statistics must be registered while initializing modules in \"shared_preload_libraries\"."))); + + /* + * Check some data for fixed-numbered stats. + */ + if (kind_info->fixed_amount) + { + if (kind_info->shared_size == 0) + ereport(ERROR, + (errmsg("custom cumulative statistics property is invalid"), + errhint("Custom cumulative statistics require a shared memory size for fixed-numbered objects."))); + } + + /* + * If pgstat_kind_custom_infos is not available yet, allocate it. + */ + if (pgstat_kind_custom_infos == NULL) + { + pgstat_kind_custom_infos = (const PgStat_KindInfo **) + MemoryContextAllocZero(TopMemoryContext, + sizeof(PgStat_KindInfo *) * PGSTAT_KIND_CUSTOM_SIZE); + } + + if (pgstat_kind_custom_infos[idx] != NULL && + pgstat_kind_custom_infos[idx]->name != NULL) + ereport(ERROR, + (errmsg("failed to register custom cumulative statistics \"%s\" with ID %u", kind_info->name, kind), + errdetail("Custom cumulative statistics \"%s\" already registered with the same ID.", + pgstat_kind_custom_infos[idx]->name))); + + /* check for existing custom stats with the same name */ + for (PgStat_Kind existing_kind = PGSTAT_KIND_CUSTOM_MIN; existing_kind <= PGSTAT_KIND_CUSTOM_MAX; existing_kind++) + { + uint32 existing_idx = existing_kind - PGSTAT_KIND_CUSTOM_MIN; + + if (pgstat_kind_custom_infos[existing_idx] == NULL) + continue; + if (!pg_strcasecmp(pgstat_kind_custom_infos[existing_idx]->name, kind_info->name)) + ereport(ERROR, + (errmsg("failed to register custom cumulative statistics \"%s\" with ID %u", kind_info->name, kind), + errdetail("Existing cumulative statistics with ID %u has the same name.", existing_kind))); + } + + /* Register it */ + pgstat_kind_custom_infos[idx] = kind_info; + ereport(LOG, + (errmsg("registered custom cumulative statistics \"%s\" with ID %u", + kind_info->name, kind))); } /* @@ -1393,18 +1555,22 @@ pgstat_write_statsfile(XLogRecPtr redo) write_chunk_s(fpout, &redo); /* Write various stats structs for fixed number of objects */ - for (PgStat_Kind kind = PGSTAT_KIND_FIRST_VALID; kind <= PGSTAT_KIND_LAST; kind++) + for (PgStat_Kind kind = PGSTAT_KIND_MIN; kind <= PGSTAT_KIND_MAX; kind++) { char *ptr; const PgStat_KindInfo *info = pgstat_get_kind_info(kind); - if (!info->fixed_amount) + if (!info || !info->fixed_amount) continue; - Assert(info->snapshot_ctl_off != 0); + if (pgstat_is_kind_builtin(kind)) + Assert(info->snapshot_ctl_off != 0); pgstat_build_snapshot_fixed(kind); - ptr = ((char *) &pgStatLocal.snapshot) + info->snapshot_ctl_off; + if (pgstat_is_kind_builtin(kind)) + ptr = ((char *) &pgStatLocal.snapshot) + info->snapshot_ctl_off; + else + ptr = pgStatLocal.snapshot.custom_data[kind - PGSTAT_KIND_CUSTOM_MIN]; fputc(PGSTAT_FILE_ENTRY_FIXED, fpout); write_chunk_s(fpout, &kind); @@ -1427,6 +1593,17 @@ pgstat_write_statsfile(XLogRecPtr redo) if (ps->dropped) continue; + /* + * This discards data related to custom stats kinds that are unknown + * to this process. + */ + if (!pgstat_is_kind_valid(ps->key.kind)) + { + elog(WARNING, "found unknown stats entry %u/%u/%u", + ps->key.kind, ps->key.dboid, ps->key.objoid); + continue; + } + shstats = (PgStatShared_Common *) dsa_get_address(pgStatLocal.dsa, ps->body); kind_info = pgstat_get_kind_info(ps->key.kind); @@ -1613,8 +1790,16 @@ pgstat_read_statsfile(XLogRecPtr redo) } /* Load back stats into shared memory */ - ptr = ((char *) shmem) + info->shared_ctl_off + - info->shared_data_off; + if (pgstat_is_kind_builtin(kind)) + ptr = ((char *) shmem) + info->shared_ctl_off + + info->shared_data_off; + else + { + int idx = kind - PGSTAT_KIND_CUSTOM_MIN; + + ptr = ((char *) shmem->custom_data[idx]) + + info->shared_data_off; + } if (!read_chunk(fpin, ptr, info->shared_data_len)) { @@ -1777,11 +1962,11 @@ pgstat_reset_after_failure(void) TimestampTz ts = GetCurrentTimestamp(); /* reset fixed-numbered stats */ - for (PgStat_Kind kind = PGSTAT_KIND_FIRST_VALID; kind <= PGSTAT_KIND_LAST; kind++) + for (PgStat_Kind kind = PGSTAT_KIND_MIN; kind <= PGSTAT_KIND_MAX; kind++) { const PgStat_KindInfo *kind_info = pgstat_get_kind_info(kind); - if (!kind_info->fixed_amount) + if (!kind_info || !kind_info->fixed_amount) continue; kind_info->reset_all_cb(ts); diff --git a/src/backend/utils/activity/pgstat_shmem.c b/src/backend/utils/activity/pgstat_shmem.c index 2d5f7d46de7..fd09b9d988b 100644 --- a/src/backend/utils/activity/pgstat_shmem.c +++ b/src/backend/utils/activity/pgstat_shmem.c @@ -131,6 +131,21 @@ StatsShmemSize(void) sz = MAXALIGN(sizeof(PgStat_ShmemControl)); sz = add_size(sz, pgstat_dsa_init_size()); + /* Add shared memory for all the custom fixed-numbered statistics */ + for (PgStat_Kind kind = PGSTAT_KIND_CUSTOM_MIN; kind <= PGSTAT_KIND_CUSTOM_MAX; kind++) + { + const PgStat_KindInfo *kind_info = pgstat_get_kind_info(kind); + + if (!kind_info) + continue; + if (!kind_info->fixed_amount) + continue; + + Assert(kind_info->shared_size != 0); + + sz += MAXALIGN(kind_info->shared_size); + } + return sz; } @@ -197,15 +212,25 @@ StatsShmemInit(void) pg_atomic_init_u64(&ctl->gc_request_count, 1); /* initialize fixed-numbered stats */ - for (PgStat_Kind kind = PGSTAT_KIND_FIRST_VALID; kind <= PGSTAT_KIND_LAST; kind++) + for (PgStat_Kind kind = PGSTAT_KIND_MIN; kind <= PGSTAT_KIND_MAX; kind++) { const PgStat_KindInfo *kind_info = pgstat_get_kind_info(kind); char *ptr; - if (!kind_info->fixed_amount) + if (!kind_info || !kind_info->fixed_amount) continue; - ptr = ((char *) ctl) + kind_info->shared_ctl_off; + if (pgstat_is_kind_builtin(kind)) + ptr = ((char *) ctl) + kind_info->shared_ctl_off; + else + { + int idx = kind - PGSTAT_KIND_CUSTOM_MIN; + + Assert(kind_info->shared_size != 0); + ctl->custom_data[idx] = ShmemAlloc(kind_info->shared_size); + ptr = ctl->custom_data[idx]; + } + kind_info->init_shmem_cb(ptr); } } diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c index 3876339ee1b..32211371237 100644 --- a/src/backend/utils/adt/pgstatfuncs.c +++ b/src/backend/utils/adt/pgstatfuncs.c @@ -1696,7 +1696,7 @@ pg_stat_reset(PG_FUNCTION_ARGS) * Reset some shared cluster-wide counters * * When adding a new reset target, ideally the name should match that in - * pgstat_kind_infos, if relevant. + * pgstat_kind_builtin_infos, if relevant. */ Datum pg_stat_reset_shared(PG_FUNCTION_ARGS) diff --git a/src/include/pgstat.h b/src/include/pgstat.h index f84e9fdeca5..f63159c55ca 100644 --- a/src/include/pgstat.h +++ b/src/include/pgstat.h @@ -35,6 +35,10 @@ /* The types of statistics entries */ #define PgStat_Kind uint32 +/* Range of IDs allowed, for built-in and custom kinds */ +#define PGSTAT_KIND_MIN 1 /* Minimum ID allowed */ +#define PGSTAT_KIND_MAX 256 /* Maximum ID allowed */ + /* use 0 for INVALID, to catch zero-initialized data */ #define PGSTAT_KIND_INVALID 0 @@ -53,9 +57,35 @@ #define PGSTAT_KIND_SLRU 10 #define PGSTAT_KIND_WAL 11 -#define PGSTAT_KIND_FIRST_VALID PGSTAT_KIND_DATABASE -#define PGSTAT_KIND_LAST PGSTAT_KIND_WAL -#define PGSTAT_NUM_KINDS (PGSTAT_KIND_LAST + 1) +#define PGSTAT_KIND_BUILTIN_MIN PGSTAT_KIND_DATABASE +#define PGSTAT_KIND_BUILTIN_MAX PGSTAT_KIND_WAL +#define PGSTAT_KIND_BUILTIN_SIZE (PGSTAT_KIND_BUILTIN_MAX + 1) + +/* Custom stats kinds */ + +/* Range of IDs allowed for custom stats kinds */ +#define PGSTAT_KIND_CUSTOM_MIN 128 +#define PGSTAT_KIND_CUSTOM_MAX PGSTAT_KIND_MAX +#define PGSTAT_KIND_CUSTOM_SIZE (PGSTAT_KIND_CUSTOM_MAX - PGSTAT_KIND_CUSTOM_MIN + 1) + +/* + * PgStat_Kind to use for extensions that require an ID, but are still in + * development and have not reserved their own unique kind ID yet. See: + * https://wiki.postgresql.org/wiki/CustomCumulativeStats + */ +#define PGSTAT_KIND_EXPERIMENTAL 128 + +static inline bool +pgstat_is_kind_builtin(PgStat_Kind kind) +{ + return kind >= PGSTAT_KIND_BUILTIN_MIN && kind <= PGSTAT_KIND_BUILTIN_MAX; +} + +static inline bool +pgstat_is_kind_custom(PgStat_Kind kind) +{ + return kind >= PGSTAT_KIND_CUSTOM_MIN && kind <= PGSTAT_KIND_CUSTOM_MAX; +} /* Values for track_functions GUC variable --- order is significant! */ typedef enum TrackFunctionsLevel diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h index 778f625ca1d..26b4b784060 100644 --- a/src/include/utils/pgstat_internal.h +++ b/src/include/utils/pgstat_internal.h @@ -195,7 +195,8 @@ typedef struct PgStat_KindInfo /* * The size of an entry in the shared stats hash table (pointed to by - * PgStatShared_HashEntry->body). + * PgStatShared_HashEntry->body). For fixed-numbered statistics, this is + * the size of an entry in PgStat_ShmemControl->custom_data. */ uint32 shared_size; @@ -446,6 +447,13 @@ typedef struct PgStat_ShmemControl PgStatShared_IO io; PgStatShared_SLRU slru; PgStatShared_Wal wal; + + /* + * Custom stats data with fixed-numbered objects, indexed by (PgStat_Kind + * - PGSTAT_KIND_CUSTOM_MIN). + */ + void *custom_data[PGSTAT_KIND_CUSTOM_SIZE]; + } PgStat_ShmemControl; @@ -459,7 +467,7 @@ typedef struct PgStat_Snapshot /* time at which snapshot was taken */ TimestampTz snapshot_timestamp; - bool fixed_valid[PGSTAT_NUM_KINDS]; + bool fixed_valid[PGSTAT_KIND_BUILTIN_SIZE]; PgStat_ArchiverStats archiver; @@ -473,6 +481,14 @@ typedef struct PgStat_Snapshot PgStat_WalStats wal; + /* + * Data in snapshot for custom fixed-numbered statistics, indexed by + * (PgStat_Kind - PGSTAT_KIND_CUSTOM_MIN). Each entry is allocated in + * TopMemoryContext, for a size of PgStat_KindInfo->shared_data_len. + */ + bool custom_valid[PGSTAT_KIND_CUSTOM_SIZE]; + void *custom_data[PGSTAT_KIND_CUSTOM_SIZE]; + /* to free snapshot in bulk */ MemoryContext context; struct pgstat_snapshot_hash *stats; @@ -516,6 +532,8 @@ static inline void *pgstat_get_entry_data(PgStat_Kind kind, PgStatShared_Common */ extern const PgStat_KindInfo *pgstat_get_kind_info(PgStat_Kind kind); +extern void pgstat_register_kind(PgStat_Kind kind, + const PgStat_KindInfo *kind_info); #ifdef USE_ASSERT_CHECKING extern void pgstat_assert_is_up(void);