| From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
|---|---|
| To: | Michael Loftis <mloftis(at)wgops(dot)com> |
| Cc: | Neil Conway <nconway(at)klamath(dot)dyndns(dot)org>, Dann Corbit <DCorbit(at)connx(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: What is wrong with hashed index usage? |
| Date: | 2002-04-23 23:54:53 |
| Message-ID: | 200204232354.g3NNsr002293@candle.pha.pa.us |
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| Lists: | pgsql-hackers |
Michael Loftis wrote:
> The benchmarks will depend mostly on the depth of the Btree. Hashes
> will be markedly faster only in the case(s) where descending into the
> tree to produce a matching leaf node would take longer than walking to
> the appropriate item in a hash.
>
> Most of the time until the btree gets deep they are nearly equivalent.
> When the tree ends up becoming many levels deep it can take longer to
> walk than the hash.
And what causes the btree to get deep? Is it just the number of rows in
the index?
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
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