#30867: Old indexes should be dropped after new ones are created.
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Reporter: Simon Charette | Owner: nobody
Type: Cleanup/optimization | Status: closed
Component: Migrations | Version: master
Severity: Normal | Resolution: wontfix
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Changes (by Simon Charette):
* status: new => closed
* resolution: => wontfix
Comment:
After a bit of investigation it looks like this would effectively add a
lot of complexity to the already complex `_alter_field` for little benefit
because the optimization is only valuable when only performing a
`(db_index=True)` to `(unique=True)` migration. If the field type is also
meant to be altered (e.g type) we certainly want to drop the index before
hand to avoid an internal rebuild with the new type which makes it hard to
determine when the optimization should be performed.
For the record I managed to get a noticeable speed up (10-15%) on
PostgreSQL when adding a unique constraint to an already indexed column
(10M rows integer).
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Ticket URL: <https://code.djangoproject.com/ticket/30867#comment:7>
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