Message-ID: <5534269A.10605@zioup.com>
Date: Sun, 19 Apr 2015 16:05:14 -0600
From: Yves Dorfsman <yves@zioup.com>
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To: pgsql-performance@postgresql.org
Subject: Re: extract(year from date) doesn't use index but maybe
 could?
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On 2015-04-19 15:33, Tom Lane wrote:
> 
>> It's possible that in the future someone will implement an optimization 
>> like this, but I'm not aware of anyone working on that and I wouldn't 
>> hold my breath.
> 
> Yeah.  In principle you could make the planner do this.  As Adam Williams
> notes nearby, there's a problem with lack of exact consistency between
> extract() semantics and straight timestamp comparisons; but you could
> handle that by extracting indexable expressions that are considered lossy,

What about functions that are simpler such as upper()/lower()?

On 9.3, this:
`select email from users where lower(first_name) = 'yves';

is not using the index on first_name (Seq Scan on first_name). This should be
easy to implement?

-- 
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gpg: 4096R/32B0F416


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