From: Andy Colson <andy@squeakycode.net>
To: Stefan Keller <sfkeller@gmail.com>
Cc: pgsql-performance@postgresql.org, Stephen Frost <sfrost@snowman.net>
Subject: Re: PG as in-memory db? How to warm up and re-populate buffers? How to read in all tuples into memory?
Date: Sun, 26 Feb 2012 13:20:58 -0600
Message-ID: <4F4A861A.3000301@squeakycode.net> (raw)
In-Reply-To: <CAFcOn2-n=fCmJEwB81V-SDo00RzTPrQbrh=GAgxoE1DWLqhtDw@mail.gmail.com>
References: <CAFcOn28A3dkmCEGsu-7Chi0gH1qAPYcfbSp8op9gswFawS6ECA@mail.gmail.com>
<4F4A4DD6.6090904@squeakycode.net>
<CAFcOn2-n=fCmJEwB81V-SDo00RzTPrQbrh=GAgxoE1DWLqhtDw@mail.gmail.com>
On 02/26/2012 01:11 PM, Stefan Keller wrote:
> 2012/2/26 Andy Colson<andy@squeakycode.net> wrote:
>> On 02/25/2012 06:16 PM, Stefan Keller wrote:
>>> 1. How can I warm up or re-populate shared buffers of Postgres?
>>> 2. Are there any hints on how to tell Postgres to read in all table
>>> contents into memory?
>>>
>>> Yours, Stefan
>>
>> How about after you load the data, vacuum freeze it, then do something like:
>>
>> SELECT count(*) FROM osm_point WHERE tags @> 'tourism=>junk'
>>
>> -Andy
>
> That good idea is what I proposed elsewhere on one of the PG lists and
> got told that this does'nt help.
>
> I can accept this approach that users should'nt directly interfere
> with the optimizer. But I think it's still worth to discuss a
> configuration option (per table) or so which tells PG that this table
> contents should fit into memory so that it tries to load a table into
> memory and keeps it there. This option probably only makes sense in
> combination with unlogged tables.
>
> Yours, Stefan
>
I don't buy that. Did you test it? Who/where did you hear this? And... how long does it take after you replace the entire table until things are good and cached? One or two queries?
After a complete reload of the data, do you vacuum freeze it?
After a complete reload of the data, how long until its fast?
-Andy
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To: pgsql-performance@postgresql.org
Cc: andy@squeakycode.net, sfkeller@gmail.com, sfrost@snowman.net
Subject: Re: PG as in-memory db? How to warm up and re-populate buffers? How to read in all tuples into memory?
In-Reply-To: <4F4A861A.3000301@squeakycode.net>
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