Re: [PERFORM] good old VACUUM FULL
On Tue, Mar 22, 2011 at 6:52 PM, felix crucialfe...@gmail.com wrote: I posted many weeks ago about a severe problem with a table that was obviously bloated and was stunningly slow. Up to 70 seconds just to get a row count on 300k rows. I removed the text column, so it really was just a few columns of fixed data. Still very bloated. Table size was 450M The advice I was given was to do CLUSTER, but this did not reduce the table size in the least. Then either cluster failed (did you get an error message) or the table was not bloated. Given that it looks like it was greatly reduced in size by the vacuum full, I'd guess cluster failed for some reason. -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
Re: [PERFORM] good old VACUUM FULL
On 03/23/2011 01:16 AM, Scott Marlowe wrote: Then either cluster failed (did you get an error message) or the table was not bloated. Given that it looks like it was greatly reduced in size by the vacuum full, I'd guess cluster failed for some reason. Or it just bloated again. Remember, he still hasn't changed his max_fsm_pages setting, and that table apparently experiences *very* high turnover. A 25x bloat factor isn't unheard of for such a table. We have one that needs to have autovacuum or be manually vacuumed frequently because it experiences several thousand update/deletes per minute. The daily turnover of that particular table is around 110x. If our fsm settings were too low, or we didn't vacuum regularly, I could easily see that table quickly becoming unmanageable. I fear for his django_session table for similar reasons. Felix, I know you don't want to experiment with kernel parameters, but you *need* to increase your max_fsm_pages setting. -- Shaun Thomas OptionsHouse | 141 W. Jackson Blvd. | Suite 800 | Chicago IL, 60604 312-676-8870 stho...@peak6.com __ See http://www.peak6.com/email_disclaimer.php for terms and conditions related to this email -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
[PERFORM] good old VACUUM FULL
I posted many weeks ago about a severe problem with a table that was obviously bloated and was stunningly slow. Up to 70 seconds just to get a row count on 300k rows. I removed the text column, so it really was just a few columns of fixed data. Still very bloated. Table size was 450M The advice I was given was to do CLUSTER, but this did not reduce the table size in the least. Nor performance. Also to resize my free space map (which still does need to be done). Since that involves tweaking the kernel settings, taking the site down and rebooting postgres and exposing the system to all kinds of risks and unknowns and expensive experimentations I was unable to do it and have had to hobble along with a slow table in my backend holding up jobs. Much swearing that nobody should ever do VACUUM FULL. Manual advises against it. Only crazy people do that. Finally I decide to stop taking advice. ns= explain analyze select count(*) from fastadder_fastadderstatus; - Aggregate (cost=62602.08..62602.09 rows=1 width=0) (actual time=25320.000..25320.000 rows=1 loops=1) - Seq Scan on fastadder_fastadderstatus (cost=0.00..61815.86 rows=314486 width=0) (actual time=180.000..25140.000 rows=314493 loops=1) Total runtime: *25320.000* ms ns= vacuum full fastadder_fastadderstatus; took about 20 minutes ns= explain analyze select count(*) from fastadder_fastadderstatus; Aggregate (cost=7478.03..7478.04 rows=1 width=0) (actual time=940.000..940.000 rows=1 loops=1) - Seq Scan on fastadder_fastadderstatus (cost=0.00..6691.82 rows=314482 width=0) (actual time=0.000..530.000 rows=314493 loops=1) Total runtime: *940.000 ms* moral of the story: if your table is really bloated, just do VACUUM FULL CLUSTER will not reduce table bloat in and identical fashion
Re: [PERFORM] good old VACUUM FULL
On 23/03/11 11:52, felix wrote: I posted many weeks ago about a severe problem with a table that was obviously bloated and was stunningly slow. Up to 70 seconds just to get a row count on 300k rows. I removed the text column, so it really was just a few columns of fixed data. Still very bloated. Table size was 450M The advice I was given was to do CLUSTER, but this did not reduce the table size in the least. Nor performance. Also to resize my free space map (which still does need to be done). Since that involves tweaking the kernel settings, taking the site down and rebooting postgres and exposing the system to all kinds of risks and unknowns and expensive experimentations I was unable to do it and have had to hobble along with a slow table in my backend holding up jobs. Much swearing that nobody should ever do VACUUM FULL. Manual advises against it. Only crazy people do that. snip moral of the story: if your table is really bloated, just do VACUUM FULL You'll need to reindex that table now - vacuum full can bloat your indexes which will affect your other queries. reindex table fastadder_fastadderstatus; -- Postgresql php tutorials http://www.designmagick.com/ -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
