From 2fb7a75f37d0beca80f45e15736ec8d50064228a Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Thu, 19 Feb 2015 21:36:50 -0500
Subject: [PATCH] Add pg_stat_get_snapshot_timestamp() to show statistics
snapshot timestamp.
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
---
doc/src/sgml/monitoring.sgml | 8 ++++++++
src/backend/utils/adt/pgstatfuncs.c | 8 ++++++++
src/include/catalog/catversion.h | 2 +-
src/include/catalog/pg_proc.h | 2 ++
src/test/regress/expected/stats.out | 10 +++++++++-
src/test/regress/sql/stats.sql | 6 +++++-
6 files changed, 33 insertions(+), 3 deletions(-)
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3ce7e80dfa2..9eaf1446a1f 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -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>
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 389ea494dbb..9964c5e1032 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -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)
diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index 9100910c5e5..7133b961514 100644
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -53,6 +53,6 @@
*/
/* yyyymmddN */
-#define CATALOG_VERSION_NO 201502181
+#define CATALOG_VERSION_NO 201502191
#endif
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 7ddb4735647..6fae8a01336 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -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_ ));
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index ec0ff6589b8..86319718591 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -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
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 646b9ac6869..16163008308 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -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
--
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