Re: very long updates very small tables

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От pasman pasmański
Тема Re: very long updates very small tables
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Msg-id AANLkTimyid196f8mU_LvvtBh72MBmvRqF=s4x73FLzP3@mail.gmail.com
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Ответ на Re: very long updates very small tables  (Lars Feistner <feistner@uni-heidelberg.de>)
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2011/3/30, Lars Feistner <feistner@uni-heidelberg.de>:
> Hello Kevin,
>
>
> On 03/29/2011 09:28 PM, Kevin Grittner wrote:
>> Lars Feistner<feistner@uni-heidelberg.de>  wrote:
>>
>>> The log tells me that certain update statements take sometimes
>>> about 3-10 minutes. But we are talking about updates on tables
>>> with 1000 to 10000 rows and updates that are supposed to update 1
>>> row.
>>
>> The top possibilities that come to my mind are:
>>
>> (1)  The tables are horribly bloated.  If autovacuum is off or not
>> aggressive enough, things can degenerate to this level.
>>
> Some tables are auto vacuumed regularly others are not. The specific
> table extjs_recentlist was never autovacuumed. So i would think that
> updates on this table should be always very slow, but they are not. Only
> every 4 or 5th day for maybe half an hour and then everything is fine
> again. And;-) there is no anti virus installed.
>> (2)  Memory is over-committed and your machine is thrashing.
>>
> We can rule this out. There is enough memory installed and the database
> is less than 500MB.
>> (3)  There are explicit LOCK commands in the software which is
>> contributing to the blocking.
> We use the the jdbc driver. The jdbc driver might do some locking but we
> don't.
>>
>> (4)  There is some external delay within the transaction, such as
>> waiting for user input while the transaction is open.
>>
> No, no user interaction within a transaction.
>> Maybe there's a combination of the above at play.  Can you rule any
>> of these out?
>>
>> -Kevin
>>
> So, i will try to get the autovacuum to be more aggressive and will
> report again if nothing changes.
>
> Thanks a lot.
> Lars
>
> --
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Lars Feistner
>
> Kompetenzzentrum für Prüfungen in der Medizin
> Medizinische Fakultät Heidelberg,
> Im Neuenheimer Feld 346, Raum 013
> 69120 Heidelberg
>
> E-Mail: feistner@uni-heidelberg.de
> Fon:   +49-6221-56-8269
> Fax:   +49-6221-56-7175
>
> WWW:   http://www.ims-m.de
>         http://www.kompmed.de
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> --
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Hi. try to log all statements for an hour and show us it. And Postgresql.conf .



------------
pasman

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