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Re: 8.x index insert performance

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Kelly Burkhart <kelly(at)tradebotsystems(dot)com>
Cc: mark(at)mark(dot)mielke(dot)cc,Merlin Moncure <merlin(dot)moncure(at)rcsonline(dot)com>,pgsql-performance(at)postgresql(dot)org
Subject: Re: 8.x index insert performance
Date: 2005-10-31 21:18:47
Message-ID: 19065.1130793527@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-performance
Kelly Burkhart <kelly(at)tradebotsystems(dot)com> writes:
> Ha!  So I'm creating an index 98% full of nulls!  Looks like this is
> easily fixed with partial indexes.

Still, though, it's not immediately clear why you'd be seeing a severe
dropoff in insert performance after 50M rows.  Even though there are
lots of nulls, I don't see why they'd behave any worse for insert speed
than real data.  One would like to think that the insert speed would
follow a nice O(log N) rule.

Are you doing the inserts all in one transaction, or several?  If
several, could you get a gprof profile of inserting the same number of
rows (say a million or so) both before and after the unexpected dropoff
occurs?

			regards, tom lane

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