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POWhy is Mysql using the wrong index?
 

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    <p>Mysql is using an index on (faver_profile_id,removed,notice_id) when it should be using the index on (faver_profile_id,removed,id). The weird thing is that for some values of faver_profile_id it does use the correct index. I can use FORCE INDEX which drastically speeds up the query, but I'd like to figure out why mysql is doing this. </p> <p>This is a new table (35m rows) copied from another table using INSERT INTO.. SELECT FROM. I did not run OPTIMIZE TABLE or ANALYZE after. Could that help?</p> <pre><code>SELECT `Item`.`id` , `Item`.`cached_image` , `Item`.`submitter_id` , `Item`.`source_title` , `Item`.`source_url` , `Item`.`source_image` , `Item`.`nudity` , `Item`.`tags` , `Item`.`width` , `Item`.`height` , `Item`.`tumblr_id` , `Item`.`tumblr_reblog_key` , `Item`.`fave_count` , `Item`.`file_size` , `Item`.`animated` , `Favorite`.`id` , `Favorite`.`created` FROM `favorites` AS `Favorite` LEFT JOIN `items` AS `Item` ON ( `Favorite`.`notice_id` = `Item`.`id` ) WHERE `faver_profile_id` =11619 AND `Favorite`.`removed` =0 AND `Item`.`removed` =0 AND `nudity` =0 ORDER BY `Favorite`.`id` DESC LIMIT 26 </code></pre> <p><b>Query execution plan:</b> "idx_notice_id_profile_id" is an index on (faver_profile_id,removed,notice_id)</p> <pre><code>1 | SIMPLE | Favorite | ref | idx_faver_idx_id,idx_notice_id_profile_id,notice_id_idx | idx_notice_id_profile_id | 4 | const,const | 15742 | Using where; Using filesort | 1 | SIMPLE | Item | eq_ref | PRIMARY | PRIMARY | 4 | gragland_imgfave.Favorite.notice_id | 1 | Using where </code></pre>
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    1. USmakeee
    1. USmakeee
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      1. VTUpMod
    1. COyou should attach the execution plan
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      1. USajreal
    2. CO@ajreal okay added above.
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      1. USmakeee
 

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