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Re: Slow insert performace, 8.3 Wal related?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Bill Preston <billpreston(at)crownepointe(dot)net>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Slow insert performace, 8.3 Wal related?
Date: 2009-01-13 01:38:38
Message-ID: 15535.1231810718@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-performance
Bill Preston <billpreston(at)crownepointe(dot)net> writes:
> I've noticed some performance problems that I am guessing are WAL 
> related based on my browsing around and wondered if someone had some 
> suggestions for tuning the WAL settings. It could also help if someone 
> just laughed at me and told me it wasn't WAL.

Consider it done ;-).  I'm not sure what your problem is but it's
unlikely to be WAL, especially not if you're using the same WAL-related
settings in 8.1 and 8.3.

Which you might not be.  The large speedup from wrapping many small
inserts into one transaction is entirely expected and should have
occurred on 8.1 as well.  I am suspicious that you were running 8.1 with
fsync off and 8.3 has it on.  Do you still have your 8.1
postgresql.conf?  Comparing all the non-defaulted settings would be the
first thing to do.

If it's not that, I'm not sure.  One cross-version difference that comes
to mind is that 8.3 is a bit stickier about implicit casting, and so it
seems conceivable that something about these queries was considered
indexable in 8.1 and is not in 8.3.  But you've not provided enough
detail to do more than speculate.

			regards, tom lane

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Subject: Re: Slow insert performace, 8.3 Wal related?
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