Re: Save Hash Indexes

From: Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
To: Dimitri Fontaine <dimitri(at)2ndquadrant(dot)fr>
Cc: PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Save Hash Indexes
Date: 2013-11-01 15:37:42
Message-ID: CAMkU=1z5rVnypCdaGieD988EoQzzmS0ga8HeA2RJbje=0a=NRA@mail.gmail.com
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On Fri, Nov 1, 2013 at 6:31 AM, Dimitri Fontaine <dimitri(at)2ndquadrant(dot)fr>wrote:

> Hi,
>
> Here's an idea: when a user ask for an Hash Index transparently build a
> BTree index over an hash function instead.
>

Could something be added to the planner so that you can just build a btree
index on a hash expression, and have the planner automatically realize it
can used for an equality query because if a=b, then md5(a)=md5(b), at least
for some data types? A general ability to recognize things like that seems
like it might have other uses as well.

Cheers,

Jeff

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