Re: Killing "stuck" queries and preventing queries from getting "stuck" - Mailing list pgsql-general

From Alban Hertroys
Subject Re: Killing "stuck" queries and preventing queries from getting "stuck"
Date
Msg-id 778964D5-3005-4FEC-82BB-15AC70019D9B@solfertje.student.utwente.nl
Whole thread Raw
In response to Killing "stuck" queries and preventing queries from getting "stuck"  (Tim Uckun <timuckun@gmail.com>)
Responses Re: Killing "stuck" queries and preventing queries from getting "stuck"
List pgsql-general
On 28 Sep 2010, at 1:41, Tim Uckun wrote:

> Sometimes some queries get "stuck" in that they run for hours and
> hours. They never stop running.  Killing the deamon does not stop the
> query from running.


You really should try to find out why they get "stuck". Killing stuck clients isn't going to solve your problem (aside
fromthe fact that you probably shouldn't be using kill -9 on them, that's like using a jackhammer on a jammed door). 

Some things to look into: Are those queries waiting on a lock by another daemon maybe? Are some of them keeping
transactionsopen for a long time without committing them (or rolling them back)? 

I recall you were having another problem (with deleting records). This all smells like you either are waiting for locks
onrecords or that the statistics used for query planning aren't reflecting the actual situation. 

Have a look in pg_locks and check the query plans of some of your more problematic queries (see: explain analyse) to
seewhat's going on there. Posting the results of those here would allow more eyes to look into your issues, in case it
isn'tobvious to you. There's some good documentation on these subjects too. 

Alban Hertroys

--
If you can't see the forest for the trees,
cut the trees and you'll see there is no forest.


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