Re: Hard limit on WAL space used (because PANIC sucks) - Mailing list pgsql-hackers

From Tom Lane
Subject Re: Hard limit on WAL space used (because PANIC sucks)
Date
Msg-id 24688.1370622797@sss.pgh.pa.us
Whole thread Raw
In response to Re: Hard limit on WAL space used (because PANIC sucks)  (Heikki Linnakangas <hlinnakangas@vmware.com>)
Responses Re: Hard limit on WAL space used (because PANIC sucks)  (Heikki Linnakangas <hlinnakangas@vmware.com>)
List pgsql-hackers
Heikki Linnakangas <hlinnakangas@vmware.com> writes:
> On 06.06.2013 17:00, Heikki Linnakangas wrote:
>> A more workable idea is to sprinkle checks in higher-level code, before
>> you hold any critical locks, to check that there is enough preallocated
>> WAL. Like, at the beginning of heap_insert, heap_update, etc., and all
>> similar indexam entry points.

> Actually, there's one place that catches most of these: LockBuffer(..., 
> BUFFER_LOCK_EXCLUSIVE). In all heap and index operations, you always 
> grab an exclusive lock on a page first, before entering the critical 
> section where you call XLogInsert.

Not only is that a horrible layering/modularity violation, but surely
LockBuffer can have no idea how much WAL space will be needed.
        regards, tom lane



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