[wp-trac] [WordPress Trac] #9720: Why the left joins in wp-include/query.php?

[WordPress Trac]

#9720: Why the left joins in wp-include/query.php?
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 Reporter:  Denis-de-Bernardy  |       Owner:  anonymous
     Type:  defect (bug)       |      Status:  new      
 Priority:  normal             |   Milestone:  2.8      
Component:  Optimization       |     Version:  2.8      
 Severity:  normal             |    Keywords:           
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 While looking into #9635, I noticed a whole bunch of left joins in the
 main queries, where a straightforward join would usually seem perfectly
 valid.

 Are there any reasons for them to be used? Asking, because imporperly used
 left joins can have devastating effects on a query's performance by
 forcing the join order.

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Ticket URL: <http://core.trac.wordpress.org/ticket/9720>
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