Re: BUG #12086: docs: prewarm: When does prewarm happen?

Hi,

On 2014-11-28 07:48:18 +0000, guettliml@thomas-guettler.de wrote:
> The following bug has been logged on the website:
>
> Bug reference:      12086
> Logged by:          Thomas Güttler
> Email address:      guettliml@thomas-guettler.de
> PostgreSQL version: 9.4beta2
> Operating system:   none
> Description:
>
> The docs of prewarm could be improved:

That's not really a bug.

> http://www.postgresql.org/docs/9.4/static/pgprewarm.html
>
> I am missing: When does the prewarm happen?

When you call the function.

> I guess it happens at server
> start. But that's just a guess. Or does postgres do prewarm every N
> minutes?

There's no automatisms running in the background or anything like that.

> Second thing I am missing: How to use this method? Please provide an
> example.

It's a function. You call it like

SELECT pg_prewarm('your_relation'); The only required parameter is the
relation, the rest is optional.

Greetings,

Andres Freund

--
 Andres Freund                       http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services