Max Number of Post Versions Supported

2 comments

1. You should set WP_POST_REVISIONS to a fixed number. If you don’t, WordPress will keep an unlimited number of revisions. See function wp_revisions_to_keep():

   function wp_revisions_to_keep( $post ) {
       $num = WP_POST_REVISIONS;
   
       if ( true === $num )
           $num = -1;
       else
           $num = intval( $num );
   
       if ( ! post_type_supports( $post->post_type, 'revisions' ) )
           $num = 0;
   
       return (int) apply_filters( 'wp_revisions_to_keep', $num, $post );
   }
   

   On the other hand … if you need such a high number of changes you should revisit the edit work flow. There are surely ways to get this number down.

2. To address:

   What will happen to these posts if I set WP_POST_REVISIONS to 10?
   Will old versions be deleted automatically, or will they remain?

   You have this action:

   add_action( 'pre_post_update', 'wp_save_post_revision' );
   

   set by default in /wp-includes/default-filters.php.

   If you check the source of wp_save_post_revision() you can see that it will delete the remaining revisions of the current post:

   $delete = count($revisions) - WP_POST_REVISIONS;
   

   with wp_delete_post_revision() when the hook pre_post_update is activated for a given $post_id, except when it is performing an auto-saving.

   Here is the relevant part from the source of wp_save_post_revision():

   // WP_POST_REVISIONS = true (default), -1
   if ( !is_numeric( WP_POST_REVISIONS ) || WP_POST_REVISIONS < 0 )
           return $return;
   
   // all revisions and (possibly) one autosave
   $revisions = wp_get_post_revisions( $post_id, array( 'order' => 'ASC' ) );
   
   // WP_POST_REVISIONS = (int) (# of autosaves to save)
   $delete = count($revisions) - WP_POST_REVISIONS;
   
   if ( $delete < 1 )
           return $return;
   
   $revisions = array_slice( $revisions, 0, $delete );
   
   for ( $i = 0; isset($revisions[$i]); $i++ ) {
           if ( false !== strpos( $revisions[$i]->post_name, 'autosave' ) )
                   continue;
           wp_delete_post_revision( $revisions[$i]->ID );
   }
   

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