Re: WAL Rate Limiting

On 2014-01-16 10:35:20 -0500, Tom Lane wrote:
> Andres Freund <andres@2ndquadrant.com> writes:
> > I don't really see much difficulty in determining what's a utility
> > command and what not for the purpose of this? All utility commands which
> > create WAL in O(table_size) or worse.
> 
> By that definition, INSERT, UPDATE, and DELETE can all be "utility
> commands".  So would a full-table-scan SELECT, if it's unfortunate
> enough to run into a lot of hint-setting or HOT-pruning work.

Well, I said *utility* command. So everything processed by
ProcessUtility() generating WAL like that.

> I think possibly a more productive approach to this would be to treat
> it as a session-level GUC setting, rather than hard-wiring it to affect
> certain commands and not others.

Do you see a reasonable way to implement this generically for all
commands? I don't.
We shouldn't let the the need for generic resource control stop us from
providing some for of resource control for a consistent subset of
commands.

Greetings,

Andres Freund

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