[wp-trac] [WordPress Trac] #15499: Add an index for get_lastpostmodified query

[WordPress Trac]

#15499: Add an index for get_lastpostmodified query
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 Reporter:  simonwheatley                        |       Owner:  (none)
     Type:  enhancement                          |      Status:  reopened
 Priority:  normal                               |   Milestone:  Awaiting
                                                 |  Review
Component:  Database                             |     Version:  3.0.1
 Severity:  normal                               |  Resolution:
 Keywords:  has-patch dev-feedback 4.1-early     |     Focuses:
  commit bulk-reopened                           |  performance
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Changes (by McBoof):

 * keywords:  has-patch, dev-feedback, 4.1-early, commit, bulk-reopened =>
     has-patch dev-feedback 4.1-early commit bulk-reopened


Comment:

 Hi there,

 Just to add something from what I'm seeing. We're running a large multi-
 tenanted WordPress setup (all on close to the latest 4.x versions at the
 moment). I've been analyzing the slow query log (showing queries longer
 than 2 secs on a large but busy MySQL RDS instance).

 This query is by far and away the worst culprit across all my databases.
 It is doing a Table Scan of often over 100,000 rows, sometimes taking 20
 seconds or so. Of the top 100 slowest query on my instance today for
 example (running about 60 databases), rougly 70% of the slowest queries
 where this one.

 From my point of view, it is certainly worth a dedicated index if this
 query is needed.

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Ticket URL: <https://core.trac.wordpress.org/ticket/15499#comment:28>
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