Re: Update in trigger

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От Jan Wieck
Тема Re: Update in trigger
Дата
Msg-id 200204041505.g34F5l807360@saturn.janwieck.net
обсуждение исходный текст
Ответ на Re: Update in trigger  (Iklódi Lajos <il@mithrandir.hu>)
Список pgsql-sql
[Ikl_di] Lajos wrote:
[Charset iso-8859-2 unsupported, filtering to ASCII...]
> Hi,
>
> Jan Wieck _rta:
>
> >     Are  there  appropriate  indexes  on the table updated in the
> >     trigger and is the database "VACUUM ANALYZE"ed so the indexes
> >     get used?
>
> There is a primary key.
> VACUUM ANALYZE is really helpful, but only for a few minutes (3000 inserted
> records).
>
>
> William Meloney _rta:
>
> > Please forward a copy of the trigger.  This is exactly the same thing I
> > am trying to do but I have not had any success.
>
> Here is the whole structure:
>
> [...]
   That's a well known problem with PostgreSQL's non-overwriting   storage management system. After your 3000 INSERTs,
you also   have UPDATEed szm 3000 times, leaving 3000 dead rows and 3000   dead index entries in it. Thus, another
UPDATE looking  for   kod=1 will find 3000 index entries and has to check 3000 data   rows only to find that they have
tobe ignored.
 
   The only way I see at the time beeing  is  to  vacuum  tables   that  have  very  few rows with a high update
frequency"very   often".  No need to vacuum the rest of the  database  at  the   same rate, just these special tables.
 


Jan

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