Re: query performance optimization
Posted by:
Rick James
Date: January 22, 2016 06:29PM
Which of these is usually the most 'selective':
SSI.is_eligible_sc>0
(SAM.admin_user_id IS NULL OR SAM.admin_user_id='24577')
(CPEI.attribute_id=133)
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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