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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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10
src/test/regress/expected/stats.out
View File

@ -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
View File

@ -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