From: | Robert Klemme <shortcutter(at)googlemail(dot)com> |
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To: | pgsql-performance <pgsql-performance(at)postgresql(dot)org> |
Subject: | Re: LIKE pattern |
Date: | 2016-05-12 15:13:18 |
Message-ID: | CAM9pMnNXnF_uEiW76eLu6yEzizpjHvuMS3sxsxNKjXLbf0CDJg@mail.gmail.com |
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Lists: | pgsql-performance |
On Mon, May 9, 2016 at 11:41 PM, SoDupuDupu wrote:
> Владимир-3 wrote
>> It seems my quite complex query runs 10 times faster on "some_column
>> LIKE '%test_1' " vs "some_column LIKE 'test_1' "
>> So I just add "%" to the pattern...
>
> Keep in mind then LIKE '%test_1' and LIKE 'test_1' are not equivalent, using
> the % as a prefix to the argument means that the scan only has to confirm
> that the value ends in 'test_1' where forgoing the % entirely means that you
> are essentially saying some_column='test_1'.
Yes, but wouldn't the latter test be more efficient usually since it
tests against a prefix - at least with a regular index?
Kind regards
robert
--
[guy, jim, charlie].each {|him| remember.him do |as, often| as.you_can
- without end}
http://blog.rubybestpractices.com/
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