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Re: extending relations more efficiently

From: Simon Riggs <simon(at)2ndQuadrant(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: extending relations more efficiently
Date: 2012-05-01 14:22:49
Message-ID: CA+U5nMLTCsZuDEUMMTTUjnERT=_RiWcirGvaOKKMGv5NmHxn7A@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Tue, May 1, 2012 at 3:08 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:

> We've previously discussed the possible desirability of extending
> relations in larger increments, rather than one block at a time, for
> performance reasons.  I attempted to determine how much performance we
> could possibly buy this way, and found that, as far as I can see, the
> answer is, basically, none.

Fair enough, but my understanding was that tests showed that the
extension lock was a bottleneck, so doing extensions in larger chunks
should reduce the time we spend waiting for a lock and thus improve
performance. So while your results here show no gain, there is gain to
be had elsewhere as a result.

The algorithm needs to be adaptive, so we don't waste space on smaller
tables or lower loads.

-- 
 Simon Riggs                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

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