My index doesn't write anymore but read

ben.play <benjamin.cohen@playrion.com> wrote:

Hi all,

We have a large database with postgre 9.3 (>300 Gb) and our queries are
(really) long for 6 days without changing anything.

After seeing our log, I saw that the same query on an old data was quick but
the same query with new data are really slow.

please provide us a explain <your query>. Please try a 'analyse
<table>'.

Andreas
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Thank you for your quick answer !

And ... you are a genius :)

A simple "analyse
" resolved my problem.
Do We have to do it regularly ?

Thank you a lot !

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ben.play <benjamin.cohen@playrion.com> wrote:

Thank you for your quick answer !

And ... you are a genius :)

Yeah, i know ;-)

A simple "analyse
" resolved my problem.
Do We have to do it regularly ?

it's running regulary (via vacuum-process), but you can (and should) run
it after mass data changes.

Andreas
--
Really, I'm not out to destroy Microsoft. That will just be a completely
unintentional side effect. (Linus Torvalds)
"If I was god, I would recompile penguin with --enable-fly." (unknown)
Kaufbach, Saxony, Germany, Europe. N 51.05082�, E 13.56889�

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Hello Ben,

Looks like you need to tune autovacuum to be more aggressive. Make sure
autovacuum=ON (the default), increase autovacuum_max_workers (at least 1
per database, more if autovacuum is falling
behind), autovacuum_vacuum_scale_factor to be ~half of the default and can
be set per table to be lower for large
tables, autovacuum_vacuum_scale_factor to be ~half of the default.

You can run the following SQL to see the last time each table was vacuumed.
If it's still not frequent enough you can try to decrease
autovacuum_naptime.
This SQL is from Bucardo's check_postgres:
SELECT current_database() AS datname,
nspname AS sname,
relname AS tname,
CASE
WHEN v IS NULL THEN -1
ELSE round(extract(epoch
FROM now()-v))
END AS ltime,
CASE
WHEN v IS NULL THEN '?'
ELSE TO_CHAR(v, 'HH24:MI FMMonth DD, YYYY')
END AS ptime
FROM
(SELECT nspname,
relname,
GREATEST(pg_stat_get_last_analyze_time(c.oid),
pg_stat_get_last_autoanalyze_time(c.oid)) AS v
FROM pg_class c,
pg_namespace n
WHERE relkind = 'r'
AND n.oid = c.relnamespace
AND n.nspname <> 'information_schema'
ORDER BY 3) AS foo;

And review the bloat of each table (should be ~1. If far above 1 vacuum is
falling behind):
SELECT schemaname,
relname,
(pg_relation_size(relid)) AS table_bytes,
n_live_tup,
n_dead_tup,
(n_live_tup::float+n_dead_tup)/n_live_tup AS bloat
FROM pg_stat_user_tables
WHERE
n_live_tup>(current_setting('autovacuum_vacuum_threshold')::bigint*10)+1;

*Will J. Dunn*
*willjdunn.com <http://willjdunn.com&gt;*

On Mon, May 18, 2015 at 3:51 AM, ben.play <benjamin.cohen@playrion.com>
wrote:

Thank your William for your help.
After 1 week, I do not see any improvement. Worse, I have to manually run
"ANALYSE" daily.
Here is my config :

My bloat for this table is 1.04151.
What does it mean exactly ?

Why do we have to analyse the table daily ? Is it normal ?

Thank you so much for your help !

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