[wp-trac] Re: [WordPress Trac] #9167: query_posts('meta_key=foo') returns duplicate posts

[WordPress Trac]

#9167: query_posts('meta_key=foo') returns duplicate posts
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 Reporter:  scribu        |       Owner:  anonymous
     Type:  defect (bug)  |      Status:  new      
 Priority:  normal        |   Milestone:  2.7.2    
Component:  General       |     Version:           
 Severity:  normal        |    Keywords:           
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Comment(by filosofo):

 I think this is a good example of why we need to bump the minimum required
 MySQL from 4.0 to at least 4.1.  MySQL 4.1 introduced sub-queries, which
 would handle well situations like this.

 Instead of the current behavior, which LEFT JOINs wp_postmeta to wp_posts
 and makes duplicate posts (something like this):

 {{{SELECT wp_posts.*, wp_postmeta.meta_value FROM wp_posts LEFT JOIN
 wp_postmeta ON (wp_posts.ID = wp_postmeta.post_id)  WHERE
 wp_postmeta.meta_key = 'some_key'}}}

 instead, we could use a sub-query and eliminate duplicate posts.

 {{{SELECT wp_posts.* FROM wp_posts WHERE wp_posts.ID IN (SELECT post_id
 FROM wp_postmeta WHERE meta_key = 'some_key')}}}

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Ticket URL: <http://core.trac.wordpress.org/ticket/9167#comment:1>
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