[wp-trac] [WordPress Trac] #24688: Memory exhaustion caused by very many unattached media

[WordPress Trac]

#24688: Memory exhaustion caused by very many unattached media
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 Reporter:  andy          |      Owner:
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  General       |    Version:  trunk
 Severity:  normal        |   Keywords:
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 A blog with over 30,000 unattached images was exhausting available memory
 on unattached attachment pages. The exhaustion occurred in
 `previous_image_link() -> adjacent_image_link() -> get_children()` due to
 the large number of rows selected with `post_parent=0`.

 This is not the only place where `get_posts()` might be called with
 `post_parent=0`. A similar query appears in
 `twentythirteen_the_attached_image()` but the effect is wisely mitigated
 by `fields=ids`. Earlier, `twentyten/loop-attachment.php` called
 `get_children()` with `post_parent=0` on unattached image pages which is
 horribly inefficient when there are many unattached images.

 Attached patch depends on #24687. The change to `adjacent_image_link()`
 creates a MySQL query which selects only the desired row. This fixes the
 memory exhaustion error on the blog with 30,000 unattached images. The
 once-only filters would be unnecessary if WP_Query accepted arbitrary
 extra WHERE strings.

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Ticket URL: <http://core.trac.wordpress.org/ticket/24688>
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