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pg_buffercache: Add pg_buffercache_summary()

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Using pg_buffercache_summary() is significantly cheaper than querying
pg_buffercache and summarizing in SQL.

Author: Melih Mutlu <m.melihmutlu@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Aleksander Alekseev <aleksander@timescale.com>
Reviewed-by: Zhang Mingli <zmlpostgres@gmail.com>
Discussion: https://postgr.es/m/CAGPVpCQAXYo54Q%3D8gqBsS%3Du0uk9qhnnq4%2B710BtUhUisX1XGEg%40mail.gmail.com
This commit is contained in:
Andres Freund
2022-10-13 09:55:46 -07:00
parent 7f8d9cedb3
commit 2589434ae0
8 changed files with 250 additions and 5 deletions
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33
contrib/pg_buffercache/expected/pg_buffercache.out
View File

@ -8,3 +8,36 @@ from pg_buffercache;
t
(1 row)
select buffers_used + buffers_unused > 0,
buffers_dirty <= buffers_used,
buffers_pinned <= buffers_used
from pg_buffercache_summary();
?column? | ?column? | ?column?
----------+----------+----------
t | t | 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;
SELECT * FROM pg_buffercache;
ERROR: permission denied for view pg_buffercache
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
RESET role;
-- Check that pg_monitor is allowed to query view / function
SET ROLE pg_monitor;
SELECT count(*) > 0 FROM pg_buffercache;
?column?
----------
t
(1 row)
SELECT buffers_used + buffers_unused > 0 FROM pg_buffercache_summary();
?column?
----------
t
(1 row)