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Re: proposal for smaller indexes on index-ordered tables

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
Cc: "Jeffrey Baker" <jwbaker(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: proposal for smaller indexes on index-ordered tables
Date: 2008-06-24 22:08:24
Message-ID: 7246.1214345304@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
"Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> writes:
> Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote: 
>> Now, *why* it is a mistake is interesting to speculate about, but
>> let's confirm the theory first.
 
> Could this be related to hint bit rewrites during indexing?

If so, changing maintenance_work_mem won't improve the situation.

What I personally suspect is that Jeff's index build is swapping like
crazy, or else there's just some problem in the sort code for such a
large sort arena.  But let's get some evidence about how the index build
time varies with maintenance_work_mem before jumping to conclusions.

> Would a vacuum between creation and indexing be a good way to tell?

Yeah, that might be a useful experiment to try too.  It wouldn't improve
the overall time AFAICS, but it would give us some idea how much of the
indexing time was really spent on hintbits.

			regards, tom lane

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Subject: Re: proposal for smaller indexes on index-ordered tables
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