[wp-trac] [WordPress Trac] #33885: meta_form performs a potentially expensive query

[WordPress Trac]

#33885: meta_form performs a potentially expensive query
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 Reporter:  jorbin                   |       Owner:
     Type:  defect (bug)             |      Status:  new
 Priority:  normal                   |   Milestone:  Future Release
Component:  Administration           |     Version:  4.3.1
 Severity:  critical                 |  Resolution:
 Keywords:  has-patch needs-testing  |     Focuses:  performance
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Comment (by matt_fw):

 Replying to [comment:39 dd32]:

 > Ideally MySQL/MariaDB/whomever else fixes whatever the bug is that we're
 running into.

 This is not a bug, it's well documented and expected behaviour
 ([https://dev.mysql.com/doc/refman/5.7/en/charset-unicode-
 conversion.html].

 The query is slow because MySQL can't use partial index on `meta_key` to
 optimize `ORDER BY` clause (at least for now). There is a workaround (
 `innodb_large_prefix` ) mentioned in the documentation I linked to but it
 requires configuration changes to MySQL so it's not general solution.

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Ticket URL: <https://core.trac.wordpress.org/ticket/33885#comment:42>
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