#35180: PostgreSQL pattern ops indexes are dropped when changing between
CharField
and TextField
-------------------------------------+-------------------------------------
Reporter: Robin Ray | Owner:
| timbaginski
Type: Bug | Status: assigned
Component: Database layer | Version: dev
(models, ORM) |
Severity: Normal | Resolution:
Keywords: index postgres | Triage Stage: Accepted
migration |
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by Natalia Bidart):
* cc: Simon Charette, Mariusz Felisiak (added)
* version: 5.0 => dev
* stage: Unreviewed => Accepted
Comment:
Hello Robin Ray, thank you for your report and for helping making Django
better.
As far as I can see, this is a valid issue. When I first read the
description, I was sure there were already similar reports so I searched a
bit for possible duplicates. I couldn't find an exact duplicate but there
are related issues reported (and fixed in some cases) in #25412, #34505,
and a few others involving collations.
It seems that the code at fault is the `_alter_field` in
`django/db/backends/postgresql/schema.py` that skips creating the index
because `old_field.db_index` and `new_field.db_index` are both True. I'm
not an expert in this area so I have added some people as cc in this
ticket, but I think this guard needs to also consider whether the column
being altered is also changing its type:
{{{#!python
diff --git a/django/db/backends/postgresql/schema.py
b/django/db/backends/postgresql/schema.py
index 842830be30..975a9f1e93 100644
--- a/django/db/backends/postgresql/schema.py
+++ b/django/db/backends/postgresql/schema.py
@@ -295,10 +295,12 @@ class
DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
new_db_params,
strict,
)
+ type_changed = old_type != new_type
+ old_db_index = old_field.db_index or old_field.unique
+ new_db_index = new_field.db_index or new_field.unique
+ needs_index = (not old_db_index and new_db_index) or
(type_changed and new_db_index)
# Added an index? Create any PostgreSQL-specific indexes.
- if (not (old_field.db_index or old_field.unique) and
new_field.db_index) or (
- not old_field.unique and new_field.unique
- ):
+ if needs_index:
like_index_statement = self._create_like_index_sql(model,
new_field)
if like_index_statement is not None:
self.execute(like_index_statement)
}}}
**NOTE:** please do not consider this diff as suitable for a patch without
further discussion.
With the patch above no test fail, so at least this is a starting point
for a conversation.
--
Ticket URL: <https://code.djangoproject.com/ticket/35180#comment:3>
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