[wp-trac] [WordPress Trac] #31388: Database Error During Upgrade

[WordPress Trac]

#31388: Database Error During Upgrade
--------------------------+-----------------------
 Reporter:  miqrogroove   |       Owner:
     Type:  defect (bug)  |      Status:  reopened
 Priority:  normal        |   Milestone:  4.2.3
Component:  Database      |     Version:  4.2
 Severity:  normal        |  Resolution:
 Keywords:                |     Focuses:
--------------------------+-----------------------
Changes (by dd32):

 * severity:  blocker => normal


Comment:

 Replying to [comment:6 jstensved]:
 > Current db_version is 29630 so when trying to upgrade line 2452 in
 upgrade.php below will first remove the index and five rows down run the
 DROP followed by ADD INDEX which breaks since the index was just removed.
 >
 > {{{
 > if ( $wp_current_db_version < 30133 ) {
 >               // dbDelta() can recreate but can't drop the index.
 >               $wpdb->query( "ALTER TABLE $wpdb->terms DROP INDEX slug"
 );
 > }
 >
 >       // Upgrade versions prior to 4.2.
 >       if ( $wp_current_db_version < 31351 ) {
 >               if ( ! is_multisite() ) {
 >                       $wpdb->query( "ALTER TABLE $wpdb->usermeta DROP
 INDEX meta_key, ADD INDEX meta_key(meta_key(191))" );
 >               }
 >               $wpdb->query( "ALTER TABLE $wpdb->terms DROP INDEX slug,
 ADD INDEX slug(slug(191))" );
 > }}}


 Confirmed that this is the most likely cause of these notices. However,
 there's a few things to note
  * This is only shown when WP_DEBUG is true (and in server logs)
  * This isn't actually a problem, only a warning
  * This only affects when updating from 4.0 or earlier.

 The current operations are in the case where this warning is shown:
  * `$wpdb->query( "ALTER TABLE $wpdb->terms DROP INDEX slug" );` -
 Succeeds
  * `$wpdb->query( "ALTER TABLE $wpdb->terms DROP INDEX slug, ADD INDEX
 slug(slug(191))" );` - Fails with warning
  * `dbDelta()` creates `slug(slug(191))` - Succeeds

 When updating from 4.1 to 4.2+ the operations are:
  * `$wpdb->query( "ALTER TABLE $wpdb->terms DROP INDEX slug, ADD INDEX
 slug(slug(191))" );` - Succeeds
  * `dbDelta()` see's that `slug(slug(191))` already exists - nothing to
 do.

 The `30133` `DROP INDEX` case just needs removing. Reducing Severity
 because this isn't actually as bad as it first seems, and it doesn't block
 anything from proceeding.

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Ticket URL: <https://core.trac.wordpress.org/ticket/31388#comment:18>
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