[3.0.x] Fixed #31106 -- Fixed migrations crash on PostgreSQL 10+ when adding FK constraints inline and changing data.

This allows adding foreign key constraints inline and changing data in
the same migration on PostgreSQL 10+.

Regression in 738faf9da2a5cd03148a36375db80746c99c9623.

Thanks Janne Rönkkö for the report and Simon Charette for the
implementation idea and review.
Backport of 22ce5d0031bd795ade081394043833e82046016c from master

1 files changed, 37 insertions, 0 deletions

diff --git a/tests/schema/tests.py b/tests/schema/tests.py
index 72476ed643..074f252197 100644
--- a/tests/schema/tests.py
+++ b/tests/schema/tests.py
@@ -275,6 +275,43 @@ class SchemaTests(TransactionTestCase):
             if sql.startswith('ALTER TABLE') and 'ADD CONSTRAINT' in sql
         ])
 
+    @skipUnlessDBFeature('can_create_inline_fk')
+    def test_add_inline_fk_update_data(self):
+        with connection.schema_editor() as editor:
+            editor.create_model(Node)
+        # Add an inline foreign key and update data in the same transaction.
+        new_field = ForeignKey(Node, CASCADE, related_name='new_fk', null=True)
+        new_field.set_attributes_from_name('new_parent_fk')
+        parent = Node.objects.create()
+        with connection.schema_editor() as editor:
+            editor.add_field(Node, new_field)
+            editor.execute('UPDATE schema_node SET new_parent_fk_id = %s;', [parent.pk])
+        self.assertIn('new_parent_fk_id', self.get_indexes(Node._meta.db_table))
+
+    @skipUnlessDBFeature(
+        'can_create_inline_fk',
+        'allows_multiple_constraints_on_same_fields',
+    )
+    @isolate_apps('schema')
+    def test_add_inline_fk_index_update_data(self):
+        class Node(Model):
+            class Meta:
+                app_label = 'schema'
+
+        with connection.schema_editor() as editor:
+            editor.create_model(Node)
+        # Add an inline foreign key, update data, and an index in the same
+        # transaction.
+        new_field = ForeignKey(Node, CASCADE, related_name='new_fk', null=True)
+        new_field.set_attributes_from_name('new_parent_fk')
+        parent = Node.objects.create()
+        with connection.schema_editor() as editor:
+            editor.add_field(Node, new_field)
+            Node._meta.add_field(new_field)
+            editor.execute('UPDATE schema_node SET new_parent_fk_id = %s;', [parent.pk])
+            editor.add_index(Node, Index(fields=['new_parent_fk'], name='new_parent_inline_fk_idx'))
+        self.assertIn('new_parent_fk_id', self.get_indexes(Node._meta.db_table))
+
     @skipUnlessDBFeature('supports_foreign_keys')
     def test_char_field_with_db_index_to_fk(self):
         # Create the table