Allow disabling alterations to global tables during upgrade.
|Reported by:||ryan||Owned by:|
Sites that have large global tables (particularly users and usermeta) as well as sites that share their user tables with bbPress and other WP installs need to be able to prevent the WP upgrade from changing those tables during upgrade. An ALTER or an unbounded DELETE or UPDATE can take a long time to complete. Large sites usually want to avoid these being run as part of the WP upgrade so they can handle it themselves. Further, if you are sharing user tables between multiple bbPress and WP installs you might want one site to be the upgrade master. Let's introduce a DO_NOT_UPGRADE_GLOBAL_TABLES define that prevents dbDelta() and the upgrade functions from doing expensive queries against global tables.