Re: Hash Indexes

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
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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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