[wp-trac] [WordPress Trac] #34560: High memory usage ( and possible server error) editing post with many/large revisions

[WordPress Trac]

#34560: High memory usage ( and possible server error) editing post with many/large
revisions
-------------------------------------+-------------------------------------
 Reporter:  pdfernhout               |       Owner:  adamsilverstein
     Type:  defect (bug)             |      Status:  assigned
 Priority:  normal                   |   Milestone:  Future Release
Component:  Revisions                |     Version:  3.6
 Severity:  major                    |  Resolution:
 Keywords:  needs-unit-tests has-    |     Focuses:  administration,
  patch dev-feedback needs-testing   |  performance
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Comment (by adamsilverstein):

 @mikeyarce thanks for the ping and offer of help. Reviewing this ticket
 after a gap of time I feel like the existing patch tried to tackle too
 much. I would like to break down the code here into several discrete
 patches to accomplish each individual fix:

 * Optimize `wp_get_post_autosave`with a direct query instead of loading
 all revisions and looping thru them to find the user's autosave
 * When determining if the revisions meta box should be shown, use a count
 query instead of loading all revisions and counting them
 * when displaying the metabox, use a direct query to determine the last
 revision, instead of loading all revisions and grabbing the last one.

 Based on previous discussions, I'm not sure
 `wp_get_post_revisions_details` is viable: because the query grabs only
 certain post details, it may result in an incomplete cache of those posts
 data, potentially causing issues for example on the revisions screen where
 additional post details are needed.

 On a related note, this ticket raises the issue of how we handle revisions
 in the block editor. Long term I envision a much more modern revisions
 integration into the editor - for now we leverage the existing revisions
 screen and mainly need to check if revisions are available (and how many),
 and the latest one.

 We use two selectors for this and we should verify these work efficiently
 even with many large revisions, looks like they leverage data from the
 REST API:

 `getCurrentPostRevisionsCount` -
 https://github.com/WordPress/gutenberg/blob/c29b729a6d107fc5a7ef53efafda126d6fbb68e0/packages/editor/src/store/selectors.js#L177-L186

 `getCurrentPostLastRevisionId` -
 https://github.com/WordPress/gutenberg/blob/c29b729a6d107fc5a7ef53efafda126d6fbb68e0/packages/editor/src/store/selectors.js#L188-L198

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Ticket URL: <https://core.trac.wordpress.org/ticket/34560#comment:68>
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