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Add pg_stat_get_snapshot_timestamp() to show statistics snapshot timestamp.

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Per discussion, this could be useful for purposes such as programmatically
detecting a nonresponding stats collector.  We already have the timestamp
anyway, it's just a matter of providing a SQL-accessible function to fetch
it.

Matt Kelly, reviewed by Jim Nasby
This commit is contained in:
Tom Lane 2015-02-19 21:36:50 -05:00
parent 634618ecd0
commit 2fb7a75f37
6 changed files with 33 additions and 3 deletions
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8
doc/src/sgml/monitoring.sgml
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@ -1709,6 +1709,14 @@ postgres 27093 0.0 0.0 30096 2752 ? Ss 11:34 0:00 postgres: ser
</entry>
</row>
<row>
<entry><literal><function>pg_stat_get_snapshot_timestamp()</function></literal><indexterm><primary>pg_stat_get_snapshot_timestamp</primary></indexterm></entry>
<entry><type>timestamp with time zone</type></entry>
<entry>
Returns the timestamp of the current statistics snapshot
</entry>
</row>
<row>
<entry><literal><function>pg_stat_clear_snapshot()</function></literal><indexterm><primary>pg_stat_clear_snapshot</primary></indexterm></entry>
<entry><type>void</type></entry>

8
src/backend/utils/adt/pgstatfuncs.c
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@ -115,6 +115,7 @@ extern Datum pg_stat_get_xact_function_calls(PG_FUNCTION_ARGS);
extern Datum pg_stat_get_xact_function_total_time(PG_FUNCTION_ARGS);
extern Datum pg_stat_get_xact_function_self_time(PG_FUNCTION_ARGS);
extern Datum pg_stat_get_snapshot_timestamp(PG_FUNCTION_ARGS);
extern Datum pg_stat_clear_snapshot(PG_FUNCTION_ARGS);
extern Datum pg_stat_reset(PG_FUNCTION_ARGS);
extern Datum pg_stat_reset_shared(PG_FUNCTION_ARGS);
@ -1682,6 +1683,13 @@ pg_stat_get_xact_function_self_time(PG_FUNCTION_ARGS)
}
/* Get the timestamp of the current statistics snapshot */
Datum
pg_stat_get_snapshot_timestamp(PG_FUNCTION_ARGS)
{
PG_RETURN_TIMESTAMPTZ(pgstat_fetch_global()->stats_timestamp);
}
/* Discard the active statistics snapshot */
Datum
pg_stat_clear_snapshot(PG_FUNCTION_ARGS)

2
src/include/catalog/catversion.h
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@ -53,6 +53,6 @@
*/
/* yyyymmddN */
#define CATALOG_VERSION_NO 201502181
#define CATALOG_VERSION_NO 201502191
#endif

2
src/include/catalog/pg_proc.h
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@ -2852,6 +2852,8 @@ DESCR("statistics: total execution time of function in current transaction, in m
DATA(insert OID = 3048 ( pg_stat_get_xact_function_self_time PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 701 "26" _null_ _null_ _null_ _null_ pg_stat_get_xact_function_self_time _null_ _null_ _null_ ));
DESCR("statistics: self execution time of function in current transaction, in msec");
DATA(insert OID = 3788 ( pg_stat_get_snapshot_timestamp PGNSP PGUID 12 1 0 0 0 f f f f t f s 0 0 1184 "" _null_ _null_ _null_ _null_ pg_stat_get_snapshot_timestamp _null_ _null_ _null_ ));
DESCR("statistics: timestamp of the current statistics snapshot");
DATA(insert OID = 2230 ( pg_stat_clear_snapshot PGNSP PGUID 12 1 0 0 0 f f f f f f v 0 0 2278 "" _null_ _null_ _null_ _null_ pg_stat_clear_snapshot _null_ _null_ _null_ ));
DESCR("statistics: discard current transaction's statistics snapshot");
DATA(insert OID = 2274 ( pg_stat_reset PGNSP PGUID 12 1 0 0 0 f f f f f f v 0 0 2278 "" _null_ _null_ _null_ _null_ pg_stat_reset _null_ _null_ _null_ ));

10
src/test/regress/expected/stats.out
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@ -28,7 +28,8 @@ SELECT pg_sleep_for('2 seconds');
CREATE TEMP TABLE prevstats AS
SELECT t.seq_scan, t.seq_tup_read, t.idx_scan, t.idx_tup_fetch,
(b.heap_blks_read + b.heap_blks_hit) AS heap_blks,
(b.idx_blks_read + b.idx_blks_hit) AS idx_blks
(b.idx_blks_read + b.idx_blks_hit) AS idx_blks,
pg_stat_get_snapshot_timestamp() as snap_ts
FROM pg_catalog.pg_stat_user_tables AS t,
pg_catalog.pg_statio_user_tables AS b
WHERE t.relname='tenk2' AND b.relname='tenk2';
@ -111,4 +112,11 @@ SELECT st.heap_blks_read + st.heap_blks_hit >= pr.heap_blks + cl.relpages,
t | t
(1 row)
SELECT pr.snap_ts < pg_stat_get_snapshot_timestamp() as snapshot_newer
FROM prevstats AS pr;
snapshot_newer
----------------
t
(1 row)
-- End of Stats Test

6
src/test/regress/sql/stats.sql
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@ -22,7 +22,8 @@ SELECT pg_sleep_for('2 seconds');
CREATE TEMP TABLE prevstats AS
SELECT t.seq_scan, t.seq_tup_read, t.idx_scan, t.idx_tup_fetch,
(b.heap_blks_read + b.heap_blks_hit) AS heap_blks,
(b.idx_blks_read + b.idx_blks_hit) AS idx_blks
(b.idx_blks_read + b.idx_blks_hit) AS idx_blks,
pg_stat_get_snapshot_timestamp() as snap_ts
FROM pg_catalog.pg_stat_user_tables AS t,
pg_catalog.pg_statio_user_tables AS b
WHERE t.relname='tenk2' AND b.relname='tenk2';
@ -81,4 +82,7 @@ SELECT st.heap_blks_read + st.heap_blks_hit >= pr.heap_blks + cl.relpages,
FROM pg_statio_user_tables AS st, pg_class AS cl, prevstats AS pr
WHERE st.relname='tenk2' AND cl.relname='tenk2';
SELECT pr.snap_ts < pg_stat_get_snapshot_timestamp() as snapshot_newer
FROM prevstats AS pr;
-- End of Stats Test