Re: Hard to Use WAS: Hard limit on WAL space

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On 06/15/2013 05:57 PM, Martijn van Oosterhout wrote:
> On Sat, Jun 15, 2013 at 12:43:10PM +0800, Craig Ringer wrote:
>> Bloat ------
>>
>> Table bloat. Table bloat has been a major issue with PostgreSQL
>> users/admins for years. Anyone care to explain to me in a simple
>> paragraph how to find out if you have table or index bloat issues
>> in your database and what to do about it? (Maybe we need
>> "pg_catalog.pg_index_bloat" and "pg_catalog.pg_table_bloat"
>> views including FILLFACTOR correction?)
>>
>> I think I'll draft up a patch to add exactly that.
>
> Nice list btw. I monitor this by using the excellent check_progres
> nagios plugin, which has stuff to check for things like this.

It's been a vital tool for me too. It probably serves as a reasonable
guide for some things we could really usefully expose in system views.
Once in core we can document them in the main user manual, making them
reasonably discoverable.

Argh. I think my TODO has some kind of horrible disease, it keeps
growing uncontrollably.

> Which makes me think that it might be possible to add some other
> checks like this, in for example pg_ctl. A big fat warning 'your
> data may be eaten' might get noticed at startup.

The users who have this kind of issue aren't the ones running pg_ctl.
They'll usually be using launchd, systemctl, upstart, sysv init
scripts, etc ... whatever, something that sends the warning straight
to the system logs that they likely never read.

I don't have tons of sympathy for these people, but I do think making
fsync=off so easy to set without understanding it is kind of like
handing a grenade to a toddler.

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