Creating redundant indexes on foreign keys for MySQL/InnoDB tables
|Reported by:||Piotr Czachur||Owned by:|
|Component:||Database layer (models, ORM)||Version:||master|
|Cc:||Triage Stage:||Ready for checkin|
|Has patch:||yes||Needs documentation:||no|
|Needs tests:||no||Patch needs improvement:||no|
During adding a foreign key contraint on InnoDB table, index is created automaticaly if it doesn't exist.
(MySQL 5.x manual)
"InnoDB requires indexes on foreign keys and referenced keys so that foreign key checks can be fast and not require a table scan. In the referencing table, there must be an index where the foreign key columns are listed as the first columns in the same order. Such an index is created on the referencing table automatically if it does not exist. (This is in contrast to some older versions, in which indexes had to be created explicitly or the creation of foreign key constraints would fail.)"
After adding FK constraint, Django creates index for every FK, which just "overwrites" index that was created in background by InnoDB engine.
It's a waist of time. It's not a big deal if you just run syncdb, but if you run unit tests waiting every time for those indexes be created is a bit annoying.
Change History (10)
comment:3 Changed 6 years ago by
|Component:||ORM aggregation → Database layer (models, ORM)|