note that UpdatedAtMixin doesn't properly work on Postgres

We can't make it work; users must use a trigger

Fixes #1

Author: bfontaine

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Bixomix Changelog
 
+## Unreleased
+
+* Document `UpdatedAtMixin`’s incompatibility with Postgres (#1)
+
 ## 0.1.0 (2023/03/30)
 
 Initial public version.

README.md

@@ -33,5 +33,6 @@ class MyModel(Base, CreatedAtMixin):
 ## Mixins
 
 * `CreatedAtMixin`: add a `created_at` datetime field that’s automatically filled with the record’s creation date
-* `UpdatedAtMixin`: add an `updated_at` datetime field that’s automatically filled with the record’s last update date
+* `UpdatedAtMixin`: add an `updated_at` datetime field that’s automatically filled with the record’s last update date.
+  Note this doesn't work on Postgres; you have to [create a trigger](https://stackoverflow.com/a/71072370/735926).
 * `CreatedUpdatedAtMixin`: combined version of the previous two mixins

bixomix/dates.py

@@ -10,7 +10,11 @@ class CreatedAtMixin:
 
 
 class UpdatedAtMixin:
-    """SQLAlchemy mixin to add an `updated_at` datetime field to a table."""
+    """
+    SQLAlchemy mixin to add an `updated_at` datetime field to a table that’s set to `NOW()` every time the row is updated.
+    Note that on Postgres this creates the column but doesn't update it.
+    See https://stackoverflow.com/a/71072370/735926 for a possible solution.
+    """
     # NOTE:
     #   server_default= tells the DB the default column value while default= sets the default value at the ORM level.
     #   onupdate= sets the value on record update at the ORM level.