Re: how to fix problem then when two queries run at the same time, it takes longer to complete then if run in sequence - Mailing list pgsql-performance

From Albert Cervera Areny
Subject Re: how to fix problem then when two queries run at the same time, it takes longer to complete then if run in sequence
Date
Msg-id 200807240938.28482.albert@sedifa.com
Whole thread Raw
In response to how to fix problem then when two queries run at the same time, it takes longer to complete then if run in sequence  (Miernik <public@public.miernik.name>)
List pgsql-performance
A Dimecres 23 Juliol 2008, Miernik va escriure:
> I have a PostgreSQL database on a very low-resource Xen virtual machine,
> 48 MB RAM. When two queries run at the same time, it takes longer to
> complete then if run in sequence. Is there perhaps a way to install
> something like a query sequencer, which would process queries in a FIFO
> manner, one at a time, even if a new query comes before the last one
> running is finished, it would not give the new query to the server
> before the one running now finishes? That would greatly improve
> performance.

You didn't mention your PostgreSQL version. Since 8.3 there's "synchronized
scans" which greatly improves performance if concurrent queries have to do a
sequential scan on the same table. Of course, if queries don't hit the same
table there'll be no improvements in performance...

>
> Any tips in general for running PostgreSQL on such low-resource machine?
>
> I have:
>
> shared_buffers = 5MB
> work_mem = 1024kB
>
> are these good values, or could perhaps changing something improve it a
> bit? Any other parameters to look at?
>
> --
> Miernik
> http://miernik.name/




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