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Re: query performance optimization
Posted by: Rick James
Date: January 22, 2016 06:29PM

Which of these is usually the most 'selective':

(SAM.admin_user_id IS NULL OR SAM.admin_user_id='24577')

We should try to make the most selective one show up first the EXPLAIN.

This look like a big typo:
GROUP BY SFO.entity_id AND SOIT.id_tags IN (2,3,8,10,11,12)

Øystein -- I used to say " OR clauses tend to prevent usage of indexes" for things like
(SAM.admin_user_id IS NULL OR SAM.admin_user_id='24577')
But then I discovered "ref_or_null". However, it does not seem to be used in his case. Can you elaborate?

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Written By
January 18, 2016 04:49AM
Re: query performance optimization
January 22, 2016 06:29PM
January 22, 2016 01:08PM
January 22, 2016 11:10PM

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