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Re: Avoiding redundant fetches of btree index metapages

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Simon Riggs <simon(at)2ndquadrant(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Avoiding redundant fetches of btree index metapages
Date: 2006-04-26 16:53:55
Message-ID: 19169.1146070435@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> Hmmm.... I'm slightly worried that frequently-churning small tables will
> be made even slower by this. What do you think?

How so?

> So we would be able to cache other items also?

Only to the extent that you can guarantee a stale cache entry isn't a
problem.  We've already done the analysis involved for the existing
metapage entries, but anything else would require more thought.  (And
more cache flush events.)

> For that case we'd save N block accesses to locate the rightmost leaf
> page.

Surely you mean log(N).

			regards, tom lane

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