Re: Save Hash Indexes

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Andrew Dunstan <andrew(at)dunslane(dot)net>
Cc: Dimitri Fontaine <dimitri(at)2ndQuadrant(dot)fr>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Save Hash Indexes
Date: 2013-11-01 14:43:58
Message-ID: 10897.1383317038@sss.pgh.pa.us
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Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
> Yeah, and there's this: I've had at least one client who switched to
> using hash indexes and got a significant benefit from it precisely
> because they aren't WAL logged. They could afford to rebuild the indexes
> in the unlikely event of a crash, but the IO gain was worth it to them.
> Neither could they have tolerated unlogged tables - they wanted crash
> safety for their data. After talking through the various options with
> them they decided this was the best choice, and it might be sad to
> remove that choice from people.

That's an interesting story, but it seems like what it points to is the
need for a general "unlogged index" feature, rather than depending on
what's universally agreed to be an implementation deficiency of hash
indexes. So it sounds like an independent topic.

regards, tom lane

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