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pg_stat_statements: Track time at which all statistics were last reset.

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This commit adds "stats_reset" column into the pg_stat_statements_info
view. This column indicates the time at which all statistics in the
pg_stat_statements view were last reset.

Per discussion, this commit also changes pg_stat_statements_info code
so that "dealloc" column is reset at the same time as "stats_reset" is reset,
i.e., whenever all pg_stat_statements entries are removed, for the sake
of consistency. Previously "dealloc" was reset only when
pg_stat_statements_reset(0, 0, 0) is called and was not reset when
pg_stat_statements_reset() with non-zero value argument discards all
entries. This was confusing.

Author: Naoki Nakamichi, Yuki Seino
Reviewed-by: Yuki Seino, Kyotaro Horiguchi, Li Japin, Fujii Masao
Discussion: https://postgr.es/m/c102cf3180d0ee73c1c5a0f7f8558322@oss.nttdata.com
This commit is contained in:
Fujii Masao 2020-12-18 10:49:58 +09:00
parent 00f690a239
commit 2e0fedf036
3 changed files with 53 additions and 16 deletions
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5
contrib/pg_stat_statements/pg_stat_statements--1.8--1.9.sql
View File

@ -5,9 +5,10 @@
--- Define pg_stat_statements_info
CREATE FUNCTION pg_stat_statements_info(
OUT dealloc bigint
OUT dealloc bigint,
OUT stats_reset timestamp with time zone
)
RETURNS bigint
RETURNS record
AS 'MODULE_PATHNAME'
LANGUAGE C STRICT VOLATILE PARALLEL SAFE;

46
contrib/pg_stat_statements/pg_stat_statements.c
View File

@ -81,6 +81,7 @@
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/memutils.h"
#include "utils/timestamp.h"
PG_MODULE_MAGIC;
@ -98,7 +99,7 @@ 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 = 0x20201126;
static const uint32 PGSS_FILE_HEADER = 0x20201218;
/* PostgreSQL major version number, changes in which invalidate all entries */
static const uint32 PGSS_PG_MAJOR_VERSION = PG_VERSION_NUM / 100;
@ -199,6 +200,7 @@ typedef struct Counters
typedef struct pgssGlobalStats
{
int64 dealloc; /* # of times entries were deallocated */
TimestampTz stats_reset; /* timestamp with all stats reset */
} pgssGlobalStats;
/*
@ -565,6 +567,7 @@ pgss_shmem_startup(void)
pgss->n_writers = 0;
pgss->gc_count = 0;
pgss->stats.dealloc = 0;
pgss->stats.stats_reset = GetCurrentTimestamp();
}
info.keysize = sizeof(pgssHashKey);
@ -1881,6 +1884,9 @@ pg_stat_statements_internal(FunctionCallInfo fcinfo,
tuplestore_donestoring(tupstore);
}
/* Number of output arguments (columns) for pg_stat_statements_info */
#define PG_STAT_STATEMENTS_INFO_COLS 2
/*
* Return statistics of pg_stat_statements.
*/
@ -1888,6 +1894,16 @@ Datum
pg_stat_statements_info(PG_FUNCTION_ARGS)
{
pgssGlobalStats stats;
TupleDesc tupdesc;
Datum values[PG_STAT_STATEMENTS_INFO_COLS];
bool nulls[PG_STAT_STATEMENTS_INFO_COLS];
/* Build a tuple descriptor for our result type */
if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
elog(ERROR, "return type must be a row type");
MemSet(values, 0, sizeof(values));
MemSet(nulls, 0, sizeof(nulls));
/* Read global statistics for pg_stat_statements */
{
@ -1898,7 +1914,10 @@ pg_stat_statements_info(PG_FUNCTION_ARGS)
SpinLockRelease(&s->mutex);
}
PG_RETURN_INT64(stats.dealloc);
values[0] = Int64GetDatum(stats.dealloc);
values[1] = TimestampTzGetDatum(stats.stats_reset);
PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
}
/*
@ -2551,21 +2570,26 @@ 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? */
if (num_entries != num_remove)
goto release_lock;
/*
* Reset global statistics for pg_stat_statements since all entries are
* removed.
*/
{
volatile pgssSharedState *s = (volatile pgssSharedState *) pgss;
TimestampTz stats_reset = GetCurrentTimestamp();
SpinLockAcquire(&s->mutex);
s->stats.dealloc = 0;
s->stats.stats_reset = stats_reset;
SpinLockRelease(&s->mutex);
}
/*
* Write new empty query file, perhaps even creating a new one to recover
* if the file was missing.

18
doc/src/sgml/pgstatstatements.sgml
View File

@ -523,6 +523,16 @@
<varname>pg_stat_statements.max</varname> were observed
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>stats_reset</structfield> <type>timestamp with time zone</type>
</para>
<para>
Time at which all statistics in the
<structname>pg_stat_statements</structname> view were last reset.
</para></entry>
</row>
</tbody>
</tgroup>
</table>
@ -549,9 +559,11 @@
specified, the default value <literal>0</literal>(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
<literal>0</literal>(invalid), it will discard all statistics including
the statistics that <structname>pg_stat_statements_info</structname>
displays. By default, this function can only be executed by superusers.
<literal>0</literal>(invalid), it will discard all statistics.
If all statistics in the <filename>pg_stat_statements</filename>
view are discarded, it will also reset the statistics in the
<structname>pg_stat_statements_info</structname> view.
By default, this function can only be executed by superusers.
Access may be granted to others using <command>GRANT</command>.
</para>
</listitem>