| From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| 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 14:49:28 |
| Message-ID: | 20131101144928.GD9385@awork2.anarazel.de |
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| Lists: | pgsql-hackers |
On 2013-11-01 09:49:57 -0400, Tom Lane wrote:
> Lastly: what real-world problem are we solving by kicking that code
> to the curb?
It makes hashed lookups much easier to use. Currently if you want
indexed access over wide columns and equality is all you need you need
to write rather awkward queries to make that happen in each query,
something like:
WHERE hash(column) = hash('value') AND column = 'value'.
So some magic that hides having to do that would be nice, even it
doesn't have O(log(n)) properties. The interesting part is that the
index gets much denser and smaller, and that the individual comparisons
are much cheaper.
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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