From 9fbc3f318d039c3e1e8614c38e40843cf8fcffde Mon Sep 17 00:00:00 2001 From: Fujii Masao Date: Thu, 26 Nov 2020 21:18:05 +0900 Subject: [PATCH] pg_stat_statements: Track number of times pgss entries were deallocated. If more distinct statements than pg_stat_statements.max are observed, pg_stat_statements entries about the least-executed statements are deallocated. This commit enables us to track the total number of times those entries were deallocated. That number can be viewed in the pg_stat_statements_info view that this commit adds. It's useful when tuning pg_stat_statements.max parameter. If it's high, i.e., the entries are deallocated very frequently, which might cause the performance regression and we can increase pg_stat_statements.max to avoid those frequent deallocations. The pg_stat_statements_info view is intended to display the statistics of pg_stat_statements module itself. Currently it has only one column "dealloc" indicating the number of times entries were deallocated. But an upcoming patch will add other columns (for example, the time at which pg_stat_statements statistics were last reset) into the view. Author: Katsuragi Yuta, Yuki Seino Reviewed-by: Fujii Masao Discussion: https://postgr.es/m/0d9f1107772cf5c3f954e985464c7298@oss.nttdata.com --- contrib/pg_stat_statements/Makefile | 2 +- .../expected/pg_stat_statements.out | 15 +++++ .../pg_stat_statements--1.8--1.9.sql | 17 ++++++ .../pg_stat_statements/pg_stat_statements.c | 59 +++++++++++++++++- .../pg_stat_statements.control | 2 +- .../sql/pg_stat_statements.sql | 6 ++ doc/src/sgml/pgstatstatements.sgml | 61 +++++++++++++++++-- src/tools/pgindent/typedefs.list | 1 + 8 files changed, 155 insertions(+), 8 deletions(-) create mode 100644 contrib/pg_stat_statements/pg_stat_statements--1.8--1.9.sql diff --git a/contrib/pg_stat_statements/Makefile b/contrib/pg_stat_statements/Makefile index 081f997d70..3ec627b956 100644 --- a/contrib/pg_stat_statements/Makefile +++ b/contrib/pg_stat_statements/Makefile @@ -6,7 +6,7 @@ OBJS = \ pg_stat_statements.o EXTENSION = pg_stat_statements -DATA = pg_stat_statements--1.4.sql \ +DATA = pg_stat_statements--1.4.sql pg_stat_statements--1.8--1.9.sql \ pg_stat_statements--1.7--1.8.sql pg_stat_statements--1.6--1.7.sql \ pg_stat_statements--1.5--1.6.sql pg_stat_statements--1.4--1.5.sql \ pg_stat_statements--1.3--1.4.sql pg_stat_statements--1.2--1.3.sql \ diff --git a/contrib/pg_stat_statements/expected/pg_stat_statements.out b/contrib/pg_stat_statements/expected/pg_stat_statements.out index 2a303a7f07..16158525ca 100644 --- a/contrib/pg_stat_statements/expected/pg_stat_statements.out +++ b/contrib/pg_stat_statements/expected/pg_stat_statements.out @@ -861,4 +861,19 @@ SELECT query, plans, calls, rows FROM pg_stat_statements ORDER BY query COLLATE SELECT query, plans, calls, rows FROM pg_stat_statements ORDER BY query COLLATE "C" | 1 | 0 | 0 (6 rows) +-- +-- access to pg_stat_statements_info view +-- +SELECT pg_stat_statements_reset(); + pg_stat_statements_reset +-------------------------- + +(1 row) + +SELECT dealloc FROM pg_stat_statements_info; + dealloc +--------- + 0 +(1 row) + DROP EXTENSION pg_stat_statements; diff --git a/contrib/pg_stat_statements/pg_stat_statements--1.8--1.9.sql b/contrib/pg_stat_statements/pg_stat_statements--1.8--1.9.sql new file mode 100644 index 0000000000..2019a4ffe0 --- /dev/null +++ b/contrib/pg_stat_statements/pg_stat_statements--1.8--1.9.sql @@ -0,0 +1,17 @@ +/* contrib/pg_stat_statements/pg_stat_statements--1.8--1.9.sql */ + +-- complain if script is sourced in psql, rather than via ALTER EXTENSION +\echo Use "ALTER EXTENSION pg_stat_statements UPDATE TO '1.9'" to load this file. \quit + +--- Define pg_stat_statements_info +CREATE FUNCTION pg_stat_statements_info( + OUT dealloc bigint +) +RETURNS bigint +AS 'MODULE_PATHNAME' +LANGUAGE C STRICT VOLATILE PARALLEL SAFE; + +CREATE VIEW pg_stat_statements_info AS + SELECT * FROM pg_stat_statements_info(); + +GRANT SELECT ON pg_stat_statements_info TO PUBLIC; diff --git a/contrib/pg_stat_statements/pg_stat_statements.c b/contrib/pg_stat_statements/pg_stat_statements.c index dd963c4644..70cfdb2c9d 100644 --- a/contrib/pg_stat_statements/pg_stat_statements.c +++ b/contrib/pg_stat_statements/pg_stat_statements.c @@ -98,7 +98,7 @@ PG_MODULE_MAGIC; #define PGSS_TEXT_FILE PG_STAT_TMP_DIR "/pgss_query_texts.stat" /* Magic number identifying the stats file format */ -static const uint32 PGSS_FILE_HEADER = 0x20171004; +static const uint32 PGSS_FILE_HEADER = 0x20201126; /* PostgreSQL major version number, changes in which invalidate all entries */ static const uint32 PGSS_PG_MAJOR_VERSION = PG_VERSION_NUM / 100; @@ -193,6 +193,14 @@ typedef struct Counters uint64 wal_bytes; /* total amount of WAL bytes generated */ } Counters; +/* + * Global statistics for pg_stat_statements + */ +typedef struct pgssGlobalStats +{ + int64 dealloc; /* # of times entries were deallocated */ +} pgssGlobalStats; + /* * Statistics per statement * @@ -222,6 +230,7 @@ typedef struct pgssSharedState Size extent; /* current extent of query file */ int n_writers; /* number of active writers to query file */ int gc_count; /* query file garbage collection cycle count */ + pgssGlobalStats stats; /* global statistics for pgss */ } pgssSharedState; /* @@ -327,6 +336,7 @@ PG_FUNCTION_INFO_V1(pg_stat_statements_1_2); PG_FUNCTION_INFO_V1(pg_stat_statements_1_3); PG_FUNCTION_INFO_V1(pg_stat_statements_1_8); PG_FUNCTION_INFO_V1(pg_stat_statements); +PG_FUNCTION_INFO_V1(pg_stat_statements_info); static void pgss_shmem_startup(void); static void pgss_shmem_shutdown(int code, Datum arg); @@ -554,6 +564,7 @@ pgss_shmem_startup(void) pgss->extent = 0; pgss->n_writers = 0; pgss->gc_count = 0; + pgss->stats.dealloc = 0; } memset(&info, 0, sizeof(info)); @@ -673,6 +684,10 @@ pgss_shmem_startup(void) entry->counters = temp.counters; } + /* Read global statistics for pg_stat_statements */ + if (fread(&pgss->stats, sizeof(pgssGlobalStats), 1, file) != 1) + goto read_error; + pfree(buffer); FreeFile(file); FreeFile(qfile); @@ -794,6 +809,10 @@ pgss_shmem_shutdown(int code, Datum arg) } } + /* Dump global statistics for pg_stat_statements */ + if (fwrite(&pgss->stats, sizeof(pgssGlobalStats), 1, file) != 1) + goto error; + free(qbuffer); qbuffer = NULL; @@ -1863,6 +1882,26 @@ pg_stat_statements_internal(FunctionCallInfo fcinfo, tuplestore_donestoring(tupstore); } +/* + * Return statistics of pg_stat_statements. + */ +Datum +pg_stat_statements_info(PG_FUNCTION_ARGS) +{ + pgssGlobalStats stats; + + /* Read global statistics for pg_stat_statements */ + { + volatile pgssSharedState *s = (volatile pgssSharedState *) pgss; + + SpinLockAcquire(&s->mutex); + stats = s->stats; + SpinLockRelease(&s->mutex); + } + + PG_RETURN_INT64(stats.dealloc); +} + /* * Estimate shared memory space needed. */ @@ -2018,6 +2057,15 @@ entry_dealloc(void) } pfree(entries); + + /* Increment the number of times entries are deallocated */ + { + volatile pgssSharedState *s = (volatile pgssSharedState *) pgss; + + SpinLockAcquire(&s->mutex); + s->stats.dealloc += 1; + SpinLockRelease(&s->mutex); + } } /* @@ -2504,6 +2552,15 @@ entry_reset(Oid userid, Oid dbid, uint64 queryid) hash_search(pgss_hash, &entry->key, HASH_REMOVE, NULL); num_remove++; } + + /* Reset global statistics for pg_stat_statements */ + { + volatile pgssSharedState *s = (volatile pgssSharedState *) pgss; + + SpinLockAcquire(&s->mutex); + s->stats.dealloc = 0; + SpinLockRelease(&s->mutex); + } } /* All entries are removed? */ diff --git a/contrib/pg_stat_statements/pg_stat_statements.control b/contrib/pg_stat_statements/pg_stat_statements.control index 65b18b11d2..2f1ce6ed50 100644 --- a/contrib/pg_stat_statements/pg_stat_statements.control +++ b/contrib/pg_stat_statements/pg_stat_statements.control @@ -1,5 +1,5 @@ # pg_stat_statements extension comment = 'track planning and execution statistics of all SQL statements executed' -default_version = '1.8' +default_version = '1.9' module_pathname = '$libdir/pg_stat_statements' relocatable = true diff --git a/contrib/pg_stat_statements/sql/pg_stat_statements.sql b/contrib/pg_stat_statements/sql/pg_stat_statements.sql index e9f5bb84e3..6f58d9d0f6 100644 --- a/contrib/pg_stat_statements/sql/pg_stat_statements.sql +++ b/contrib/pg_stat_statements/sql/pg_stat_statements.sql @@ -358,4 +358,10 @@ SELECT 42; SELECT 42; SELECT query, plans, calls, rows FROM pg_stat_statements ORDER BY query COLLATE "C"; +-- +-- access to pg_stat_statements_info view +-- +SELECT pg_stat_statements_reset(); +SELECT dealloc FROM pg_stat_statements_info; + DROP EXTENSION pg_stat_statements; diff --git a/doc/src/sgml/pgstatstatements.sgml b/doc/src/sgml/pgstatstatements.sgml index cf2d25b7b2..81915ea69b 100644 --- a/doc/src/sgml/pgstatstatements.sgml +++ b/doc/src/sgml/pgstatstatements.sgml @@ -23,7 +23,9 @@ When pg_stat_statements is loaded, it tracks statistics across all databases of the server. To access and manipulate - these statistics, the module provides a view, pg_stat_statements, + these statistics, the module provides views + pg_stat_statements and + pg_stat_statements_info, and the utility functions pg_stat_statements_reset and pg_stat_statements. These are not available globally but can be enabled for a specific database with @@ -480,6 +482,52 @@ + + The <structname>pg_stat_statements_info</structname> View + + + pg_stat_statements_info + + + + The statistics of the pg_stat_statements module + itself are tracked and made available via a view named + pg_stat_statements_info. This view contains + only a single row. The columns of the view are shown in + . + + + + <structname>pg_stat_statements_info</structname> Columns + + + + + Column Type + + + Description + + + + + + + + dealloc bigint + + + Total number of times pg_stat_statements + entries about the least-executed statements were deallocated + because more distinct statements than + pg_stat_statements.max were observed + + + + +
+ + Functions @@ -501,9 +549,10 @@ specified, the default value 0(invalid) is used for each of them and the statistics that match with other parameters will be reset. If no parameter is specified or all the specified parameters are - 0(invalid), it will discard all statistics. By - default, this function can only be executed by superusers. Access may be - granted to others using GRANT. + 0(invalid), it will discard all statistics including + the statistics that pg_stat_statements_info + displays. By default, this function can only be executed by superusers. + Access may be granted to others using GRANT. @@ -555,7 +604,9 @@ statements tracked by the module (i.e., the maximum number of rows in the pg_stat_statements view). If more distinct statements than that are observed, information about the least-executed - statements is discarded. + statements is discarded. The number of times such information was + discarded can be seen in the + pg_stat_statements_info view. The default value is 5000. This parameter can only be set at server start. diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 4c40ae37b2..b8ca8cffd9 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -3215,6 +3215,7 @@ pgpid_t pgsocket pgsql_thing_t pgssEntry +pgssGlobalStats pgssHashKey pgssJumbleState pgssLocationLen