| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> |
| Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Peter Geoghegan <pg(at)heroku(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com> |
| Subject: | Re: Hard limit on WAL space used (because PANIC sucks) |
| Date: | 2013-06-07 16:33:17 |
| Message-ID: | 24688.1370622797@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Heikki Linnakangas <hlinnakangas(at)vmware(dot)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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