Re: gsoc08, text search selectivity, pg_statistics holding an array of a different type

From: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Heikki Linnakangas <heikki(at)enterprisedb(dot)com>, Jan Urbański <j(dot)urbanski(at)students(dot)mimuw(dot)edu(dot)pl>, Postgres - Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: gsoc08, text search selectivity, pg_statistics holding an array of a different type
Date: 2008-05-10 03:06:54
Message-ID: 20080510030654.GA388@alvh.no-ip.org
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Tom Lane wrote:

> Jan's right: this is an oversight in the design of the VacAttrStats API.
> The existing pg_statistics "slot" types all need an array of the same
> datatype as the underlying column, but it's obvious when you think about
> it that there could be kinds of statistics that need to be stored as an
> array of some other type. I'm good with the idea of extending
> VacAttrStats for the purpose.

Perhaps we would also want the ability to store the base element type
when the column is an array. So for a 1D int[] column, we would store
a 1D array in pg_statistics instead of a 2D array. Modules like intagg
may find some use to that ability.

I point this out because it also says that instead of inventing "most
common lexeme" we want to turn into the more generic "most common
element" or something like that.

--
Alvaro Herrera http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

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