#35180: PostgreSQL pattern ops indexes are dropped when changing between
CharField
and TextField
-------------------------------------+-------------------------------------
Reporter: Robin Ray | Owner: nobody
Type: Bug | Status: new
Component: Database | Version: 5.0
layer (models, ORM) | Keywords: index postgres
Severity: Normal | migration
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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When converting an indexed CharField to a TextField (and vice versa) on
PostgreSQL, Django drops the existing pattern ops `_like` index for the
column but does not recreate it with the new pattern ops. When reversing
the migration, Django does not recreate the initial `_like` index.
I have been able to reproduce this behavior in Django 3.2 and 5.0.
**Reproduction**
1. Given a model with a CharField that has `db_index=True` on a PostgreSQL
database
2. Inspect the database indexes or migration SQL and see that the indexed
CharField has two indexes, one of which ends in `_like` and uses
`varchar_pattern_ops`
3. Change the CharField to a TextField and generate a migration
4. Run the migration or inspect the SQL with the `sqlmigrate` manage
command
5. Inspect the database indexes or migration SQL and see that the indexed
TextField does not have a `_like` index
6. Reverse the migration
7. Inspect the database indexes or migration SQL and see that the indexed
CharField no longer has a `_like` index
Here is an example project that demonstratest the issue:
https://github.com/robin-ray/alter_text_index_repro
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Ticket URL: <https://code.djangoproject.com/ticket/35180>
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