On 2014-01-16 09:06:30 -0500, Robert Haas wrote:
> > Seems like a really bad name if we are only slowing down some commands -
> > that seems to indicate we're slowing down all of them. I think it should be
> > something that indicates that it only affects the maintenance commands.
> And why should it only affect the maintenance commands anyway, and who
> decides what's a maintenance command?

I think implementing it for everything might have some use, but it's a
much, much more complex task. You can't simply do rate limiting in
XLogInsert() or somesuch - we're holding page locks, buffer pins, other
locks... I don't see why that needs to be done in the same feature.

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.

> I thought Heroku suggested something like this previously, and their
> use case was something along the lines of "we need to slow the system
> down enough to do a backup so we can delete some stuff before the disk
> fills".  For that, it seems likely to me that you would just want to
> slow everything down.

I think the usecase for this more along the lines of not slowing normal
operations or cause replication delays to standbys unduly, while
performing maintenance operations on relations.


Andres Freund

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

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