| From: | Oskari Saarenmaa <os(at)ohmu(dot)fi> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us> |
| Cc: | Andres Freund <andres(at)anarazel(dot)de>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Hash Indexes |
| Date: | 2016-09-21 16:49:15 |
| Message-ID: | 0d6da21f-7d1c-0eda-5ed8-6157aab98367@ohmu.fi |
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| Lists: | pgsql-hackers |
21.09.2016, 15:29, Robert Haas kirjoitti:
> For PostgreSQL, I expect the benefits of improving hash indexes to be
> (1) slightly better raw performance for equality comparisons and (2)
> better concurrency.
There's a third benefit: with large columns a hash index is a lot
smaller on disk than a btree index. This is the biggest reason I've
seen people want to use hash indexes instead of btrees. hashtext()
btrees are a workaround, but they require all queries to be adjusted
which is a pain.
/ Oskari
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