[wp-trac] [WordPress Trac] #54016: Media Library: Bulk delete elements in grid view takes very long

[WordPress Trac]

#54016: Media Library: Bulk delete elements in grid view takes very long
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 Reporter:  Presskopp    |       Owner:  (none)
     Type:  enhancement  |      Status:  new
 Priority:  normal       |   Milestone:  Awaiting Review
Component:  Media        |     Version:
 Severity:  normal       |  Resolution:
 Keywords:               |     Focuses:  performance
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Comment (by lukasbesch):

 One problem in the bulk deletion process is that for every single media
 item that is deleted, a request to admin-ajax is made. That can overload
 the server pretty quickly.

 **How about we bundle these request to single one with all the IDs?**

 If we do that, the single request would probably take longer and could
 timeout. To solve that problem, we could first mark all the items as "to
 be deleted" (using the post_status) and run a scheduled job to clean up
 everything in chunks again.

 I am having this problem on a large site and found out that during the
 deletion, also the postmeta table is scanned for the _thumbnail_id and the
 corresponding entries are deleted. This is also slow on huge postmeta
 tables.

 So I imagine the process like that:
 1. A request with all attachment IDs that should be deleted is sent.
 2. These attachments get the post status `deleting`. They do not appear in
 the media view anymore or at least cannot be selected. The filename is
 still blocked for new uploads.
 3. A scheduled job picks up these attachments and deletes them (one by one
 or in chunks, oldest first?) and all relations like `_thumbnail_id`.

 … maybe this should be opt-in or a plugin? Because not everyone has large
 sites and a proper cronjob running, thus it would affect the (uncached)
 frontend in terms of performance.

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Ticket URL: <https://core.trac.wordpress.org/ticket/54016#comment:4>
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