Fix Language foreign key column lengths

contentcuration/contentcuration/migrations/0155_fix_language_foreign_key_length.py

@@ -0,0 +1,47 @@
+# Generated manually to fix Language foreign key column length in M2M junction table
+# See https://github.com/learningequality/studio/issues/5618
+#
+# When Language.id was changed from max_length=7 to max_length=14 in migration
+# 0081, Django 1.9 did not cascade the primary key column size change to the
+# many-to-many junction table column. This migration fixes that column for
+# databases that were created before the migration squash.
+#
+# This migration is idempotent - it only alters the column if it is still varchar(7).
+from django.db import migrations
+
+
+# SQL to fix the column, checking if it needs to be altered first
+FORWARD_SQL = """
+DO $$
+BEGIN
+    -- Fix contentcuration_channel_included_languages.language_id (M2M junction table)
+    IF EXISTS (
+        SELECT 1 FROM information_schema.columns
+        WHERE table_schema = 'public'
+        AND table_name = 'contentcuration_channel_included_languages'
+        AND column_name = 'language_id'
+        AND character_maximum_length = 7
+    ) THEN
+        ALTER TABLE contentcuration_channel_included_languages
+            ALTER COLUMN language_id TYPE varchar(14);
+    END IF;
+END $$;
+"""
+
+# Reverse SQL is a no-op since we don't want to shrink the columns back
+# (that could cause data loss if longer language codes have been inserted)
+REVERSE_SQL = """
+-- No-op: Cannot safely reverse this migration as it may cause data loss
+SELECT 1;
+"""
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("contentcuration", "0154_alter_assessmentitem_type"),
+    ]
+
+    operations = [
+        migrations.RunSQL(FORWARD_SQL, REVERSE_SQL),
+    ]

contentcuration/contentcuration/tests/test_language_fk_column_length_migration.py

@@ -0,0 +1,73 @@
+"""
+Test for migration 0155_fix_language_foreign_key_length.
+
+This test verifies that the migration correctly fixes the Language foreign key
+column in the included_languages M2M junction table from varchar(7) to varchar(14).
+"""
+from django.db import connection
+from django.db.migrations.executor import MigrationExecutor
+from django.test import TransactionTestCase
+
+
+# The M2M junction table column that should be fixed by the migration
+TABLE_NAME = "contentcuration_channel_included_languages"
+COLUMN_NAME = "language_id"
+
+
+def get_column_max_length(table_name, column_name):
+    """Get the character_maximum_length for a varchar column."""
+    with connection.cursor() as cursor:
+        cursor.execute(
+            """
+            SELECT character_maximum_length
+            FROM information_schema.columns
+            WHERE table_schema = 'public'
+            AND table_name = %s
+            AND column_name = %s
+            """,
+            [table_name, column_name],
+        )
+        row = cursor.fetchone()
+        return row[0] if row else None
+
+
+def set_column_to_varchar7(table_name, column_name):
+    """Shrink a varchar column to varchar(7) to simulate bad production state."""
+    with connection.cursor() as cursor:
+        cursor.execute(
+            f"ALTER TABLE {table_name} ALTER COLUMN {column_name} TYPE varchar(7)"
+        )
+
+
+class TestLanguageForeignKeyLengthMigration(TransactionTestCase):
+    """
+    Test that migration 0155 fixes varchar(7) Language FK column to varchar(14).
+
+    This simulates the production database state where Language.id was changed
+    from max_length=7 to max_length=14, but Django 1.9 didn't cascade the change
+    to the M2M junction table column.
+    """
+
+    def test_migration_fixes_varchar7_column(self):
+        # First, shrink column back to varchar(7) to simulate bad state
+        set_column_to_varchar7(TABLE_NAME, COLUMN_NAME)
+        # Verify the column is now varchar(7)
+        self.assertEqual(
+            get_column_max_length(TABLE_NAME, COLUMN_NAME),
+            7,
+            f"{TABLE_NAME}.{COLUMN_NAME} should be varchar(7) before migration",
+        )
+
+        # Run migration 0155
+        executor = MigrationExecutor(connection)
+        executor.migrate([("contentcuration", "0154_alter_assessmentitem_type")])
+        executor = MigrationExecutor(connection)
+        executor.loader.build_graph()
+        executor.migrate([("contentcuration", "0155_fix_language_foreign_key_length")])
+
+        # Verify column is now varchar(14)
+        self.assertEqual(
+            get_column_max_length(TABLE_NAME, COLUMN_NAME),
+            14,
+            f"{TABLE_NAME}.{COLUMN_NAME} should be varchar(14) after migration",
+        )