Re: Index-only scans - Mailing list pgsql-hackers

From Bruce Momjian
Subject Re: Index-only scans
Date
Msg-id 200907131338.n6DDcIP00317@momjian.us
Whole thread Raw
In response to Index-only scans  (Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>)
Responses Re: Index-only scans  (Mischa Sandberg <mischa.sandberg@sophos.com>)
Re: Index-only scans  (Peter Eisentraut <peter_e@gmx.net>)
List pgsql-hackers
Heikki Linnakangas wrote:
> Even if we don't solve the visibility
> map problem, just allowing the executor to evaluate quals that are not
> directly indexable using data from the index, would be useful. For
> example, "SELECT * FROM foo WHERE textcol LIKE '%bar%', and you have a
> b-tree index on textcol, the planner could choose a full-index-scan,
> apply the '%bar%' filter on the index tuples, and only fetch those heap
> tuples that match that qual.

Interesting, I had not considered that.  You are using the index as a
single-column table that can be scanned more quickly than the heap.

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
 + If your life is a hard drive, Christ can be your backup. +


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