diff --git a/contrib/pg_buffercache/expected/pg_buffercache.out b/contrib/pg_buffercache/expected/pg_buffercache.out index 635f01e3b2..b745dc69ea 100644 --- a/contrib/pg_buffercache/expected/pg_buffercache.out +++ b/contrib/pg_buffercache/expected/pg_buffercache.out @@ -17,6 +17,12 @@ from pg_buffercache_summary(); t | t | t (1 row) +SELECT count(*) > 0 FROM pg_buffercache_usage_counts() WHERE buffers >= 0; + ?column? +---------- + t +(1 row) + -- Check that the functions / views can't be accessed by default. To avoid -- having to create a dedicated user, use the pg_database_owner pseudo-role. SET ROLE pg_database_owner; @@ -26,6 +32,8 @@ SELECT * FROM pg_buffercache_pages() AS p (wrong int); ERROR: permission denied for function pg_buffercache_pages SELECT * FROM pg_buffercache_summary(); ERROR: permission denied for function pg_buffercache_summary +SELECT * FROM pg_buffercache_usage_counts(); +ERROR: permission denied for function pg_buffercache_usage_counts RESET role; -- Check that pg_monitor is allowed to query view / function SET ROLE pg_monitor; @@ -41,3 +49,9 @@ SELECT buffers_used + buffers_unused > 0 FROM pg_buffercache_summary(); t (1 row) +SELECT count(*) > 0 FROM pg_buffercache_usage_counts(); + ?column? +---------- + t +(1 row) + diff --git a/contrib/pg_buffercache/pg_buffercache--1.3--1.4.sql b/contrib/pg_buffercache/pg_buffercache--1.3--1.4.sql index 8f212dc5e9..d5aebf3ba3 100644 --- a/contrib/pg_buffercache/pg_buffercache--1.3--1.4.sql +++ b/contrib/pg_buffercache/pg_buffercache--1.3--1.4.sql @@ -12,6 +12,17 @@ CREATE FUNCTION pg_buffercache_summary( AS 'MODULE_PATHNAME', 'pg_buffercache_summary' LANGUAGE C PARALLEL SAFE; +CREATE FUNCTION pg_buffercache_usage_counts( + OUT usage_count int4, + OUT buffers int4, + OUT dirty int4, + OUT pinned int4) +RETURNS SETOF record +AS 'MODULE_PATHNAME', 'pg_buffercache_usage_counts' +LANGUAGE C PARALLEL SAFE; + -- Don't want these to be available to public. REVOKE ALL ON FUNCTION pg_buffercache_summary() FROM PUBLIC; GRANT EXECUTE ON FUNCTION pg_buffercache_summary() TO pg_monitor; +REVOKE ALL ON FUNCTION pg_buffercache_usage_counts() FROM PUBLIC; +GRANT EXECUTE ON FUNCTION pg_buffercache_usage_counts() TO pg_monitor; diff --git a/contrib/pg_buffercache/pg_buffercache_pages.c b/contrib/pg_buffercache/pg_buffercache_pages.c index 1c6a2f22ca..3316732365 100644 --- a/contrib/pg_buffercache/pg_buffercache_pages.c +++ b/contrib/pg_buffercache/pg_buffercache_pages.c @@ -18,6 +18,7 @@ #define NUM_BUFFERCACHE_PAGES_MIN_ELEM 8 #define NUM_BUFFERCACHE_PAGES_ELEM 9 #define NUM_BUFFERCACHE_SUMMARY_ELEM 5 +#define NUM_BUFFERCACHE_USAGE_COUNTS_ELEM 4 PG_MODULE_MAGIC; @@ -61,6 +62,7 @@ typedef struct */ PG_FUNCTION_INFO_V1(pg_buffercache_pages); PG_FUNCTION_INFO_V1(pg_buffercache_summary); +PG_FUNCTION_INFO_V1(pg_buffercache_usage_counts); Datum pg_buffercache_pages(PG_FUNCTION_ARGS) @@ -304,3 +306,44 @@ pg_buffercache_summary(PG_FUNCTION_ARGS) PG_RETURN_DATUM(result); } + +Datum +pg_buffercache_usage_counts(PG_FUNCTION_ARGS) +{ + ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo; + int usage_counts[BM_MAX_USAGE_COUNT + 1] = {0}; + int dirty[BM_MAX_USAGE_COUNT + 1] = {0}; + int pinned[BM_MAX_USAGE_COUNT + 1] = {0}; + Datum values[NUM_BUFFERCACHE_USAGE_COUNTS_ELEM]; + bool nulls[NUM_BUFFERCACHE_USAGE_COUNTS_ELEM] = {0}; + + InitMaterializedSRF(fcinfo, 0); + + for (int i = 0; i < NBuffers; i++) + { + BufferDesc *bufHdr = GetBufferDescriptor(i); + uint32 buf_state = pg_atomic_read_u32(&bufHdr->state); + int usage_count; + + usage_count = BUF_STATE_GET_USAGECOUNT(buf_state); + usage_counts[usage_count]++; + + if (buf_state & BM_DIRTY) + dirty[usage_count]++; + + if (BUF_STATE_GET_REFCOUNT(buf_state) > 0) + pinned[usage_count]++; + } + + for (int i = 0; i < BM_MAX_USAGE_COUNT + 1; i++) + { + values[0] = Int32GetDatum(i); + values[1] = Int32GetDatum(usage_counts[i]); + values[2] = Int32GetDatum(dirty[i]); + values[3] = Int32GetDatum(pinned[i]); + + tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls); + } + + return (Datum) 0; +} diff --git a/contrib/pg_buffercache/sql/pg_buffercache.sql b/contrib/pg_buffercache/sql/pg_buffercache.sql index 2e2e0a7451..944fbb1bea 100644 --- a/contrib/pg_buffercache/sql/pg_buffercache.sql +++ b/contrib/pg_buffercache/sql/pg_buffercache.sql @@ -10,15 +10,19 @@ select buffers_used + buffers_unused > 0, buffers_pinned <= buffers_used from pg_buffercache_summary(); +SELECT count(*) > 0 FROM pg_buffercache_usage_counts() WHERE buffers >= 0; + -- Check that the functions / views can't be accessed by default. To avoid -- having to create a dedicated user, use the pg_database_owner pseudo-role. SET ROLE pg_database_owner; SELECT * FROM pg_buffercache; SELECT * FROM pg_buffercache_pages() AS p (wrong int); SELECT * FROM pg_buffercache_summary(); +SELECT * FROM pg_buffercache_usage_counts(); RESET role; -- Check that pg_monitor is allowed to query view / function SET ROLE pg_monitor; SELECT count(*) > 0 FROM pg_buffercache; SELECT buffers_used + buffers_unused > 0 FROM pg_buffercache_summary(); +SELECT count(*) > 0 FROM pg_buffercache_usage_counts(); diff --git a/doc/src/sgml/pgbuffercache.sgml b/doc/src/sgml/pgbuffercache.sgml index f49d197c5f..43c52e3829 100644 --- a/doc/src/sgml/pgbuffercache.sgml +++ b/doc/src/sgml/pgbuffercache.sgml @@ -22,9 +22,10 @@ - The module provides the pg_buffercache_pages() - function, wrapped in the pg_buffercache view, and - the pg_buffercache_summary() function. + This module provides the pg_buffercache_pages() + function (wrapped in the pg_buffercache view), + the pg_buffercache_summary() function, and the + pg_buffercache_usage_counts() function. @@ -39,6 +40,12 @@ row summarizing the state of the shared buffer cache. + + The pg_buffercache_usage_counts() function returns a set + of records, each row describing the number of buffers with a given usage + count. + + By default, use is restricted to superusers and roles with privileges of the pg_monitor role. Access may be granted to others @@ -243,7 +250,7 @@ usagecount_avg float8 - Average usagecount of used shared buffers + Average usage count of used shared buffers @@ -266,6 +273,84 @@ + + The <function>pg_buffercache_usage_counts()</function> Function + + + The definitions of the columns exposed by the function are shown in + . + + + + <function>pg_buffercache_usage_counts()</function> Output Columns + + + + + Column Type + + + Description + + + + + + + + usage_count int4 + + + A possible buffer usage count + + + + + + buffers int4 + + + Number of buffers with the usage count + + + + + + dirty int4 + + + Number of dirty buffers with the usage count + + + + + + pinned int4 + + + Number of pinned buffers with the usage count + + + + +
+ + + The pg_buffercache_usage_counts() function returns a + set of rows summarizing the states of all shared buffers, aggregated over + the possible usage count values. Similar and more detailed information is + provided by the pg_buffercache view, but + pg_buffercache_usage_counts() is significantly cheaper. + + + + Like the pg_buffercache view, + pg_buffercache_usage_counts() does not acquire buffer + manager locks. Therefore concurrent activity can lead to minor inaccuracies + in the result. + + + Sample Output @@ -300,6 +385,18 @@ regression=# SELECT * FROM pg_buffercache_summary(); --------------+----------------+---------------+----------------+---------------- 248 | 2096904 | 39 | 0 | 3.141129 (1 row) + + +regression=# SELECT * FROM pg_buffercache_usage_counts(); + usage_count | buffers | dirty | pinned +-------------+---------+-------+-------- + 0 | 14650 | 0 | 0 + 1 | 1436 | 671 | 0 + 2 | 102 | 88 | 0 + 3 | 23 | 21 | 0 + 4 | 9 | 7 | 0 + 5 | 164 | 106 | 0 +(6 rows)