[wp-trac] [WordPress Trac] #30261: Split all existing shared taxonomy terms on WP upgrade

[WordPress Trac]

#30261: Split all existing shared taxonomy terms on WP upgrade
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 Reporter:  boonebgorges             |       Owner:  boonebgorges
     Type:  enhancement              |      Status:  reopened
 Priority:  high                     |   Milestone:  4.3
Component:  Taxonomy                 |     Version:
 Severity:  blocker                  |  Resolution:
 Keywords:  has-patch needs-testing  |     Focuses:
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Comment (by boonebgorges):

 Let's try this again. [attachment:30261.7.diff] simplifies the term
 splitting process by divorcing it altogether from the database upgrade.
 When a user with 'edit_posts' visits a wp-admin page (`'admin_footer'`),
 `wp_batch_split_terms()` splits 20 shared terms. This happens over and
 over again until no more shared terms are found, at which point the
 'shared_terms_split' flag is set, and the routine is never run again.

 This strategy pretty much eliminates the possibility of out-of-memory or
 timeout fatal errors, since we're only processing a small number of shared
 terms on a given pageload. As such, it all but eliminates the possibility
 of corrupt '_split_terms' back-compat data. It also means we don't need to
 futz with wp-admin/upgrade.php at all, since plugins are loaded during
 normal wp-admin pageloads. Fault tolerance is built in: it will keep
 splitting until it's finished.

 Potential downsides:
 - Precedent: I can't think of anywhere in WP where we do anything like
 this :)
 - Time: I estimate that for 95%+ of all WP installations, there will be
 fewer than 20 shared terms, so that the splitting will take place on the
 first pageload after the db upgrade (generally, about.php). But in some
 cases, it'll take more batches. Depending on wp-admin traffic, there may
 be some time - hours, days - where not all shared terms are split. IMO,
 this is not a serious issue, since we're not yet doing anything that
 requires terms to be split.

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Ticket URL: <https://core.trac.wordpress.org/ticket/30261#comment:45>
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