From 579909a13feb958f75d1d77e9995cef8f2b9c2a3 Mon Sep 17 00:00:00 2001
From: Mariusz Felisiak <felisiak.mariusz@gmail.com>
Date: Mon, 26 Aug 2019 09:15:37 +0200
Subject: [PATCH] Refs #30591 -- Fixed introspection of check and unique column
 constraints on MariaDB.

Unnamed unique and check columns constraints have the same name as
a column. Ensure uniqueness by using custom names.

Thanks Adnan Umer for the report.
---
 django/db/backends/mysql/introspection.py | 10 +++++++++-
 tests/introspection/models.py             |  1 +
 tests/introspection/tests.py              |  6 ++++++
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/django/db/backends/mysql/introspection.py b/django/db/backends/mysql/introspection.py
index 05e73c78dc..82637d15fb 100644
--- a/django/db/backends/mysql/introspection.py
+++ b/django/db/backends/mysql/introspection.py
@@ -207,6 +207,7 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
                 constraints[constraint]['unique'] = True
         # Add check constraints.
         if self.connection.features.can_introspect_check_constraints:
+            unnamed_constraints_index = 0
             columns = {info.name for info in self.get_table_description(cursor, table_name)}
             type_query = """
                 SELECT c.constraint_name, c.check_clause
@@ -217,8 +218,15 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
             """
             cursor.execute(type_query, [table_name])
             for constraint, check_clause in cursor.fetchall():
+                constraint_columns = self._parse_constraint_columns(check_clause, columns)
+                # Ensure uniqueness of unnamed constraints. Unnamed unique
+                # and check columns constraints have the same name as
+                # a column.
+                if set(constraint_columns) == {constraint}:
+                    unnamed_constraints_index += 1
+                    constraint = '__unnamed_constraint_%s__' % unnamed_constraints_index
                 constraints[constraint] = {
-                    'columns': self._parse_constraint_columns(check_clause, columns),
+                    'columns': constraint_columns,
                     'primary_key': False,
                     'unique': False,
                     'index': False,
diff --git a/tests/introspection/models.py b/tests/introspection/models.py
index 6f43359dd4..c3f6338176 100644
--- a/tests/introspection/models.py
+++ b/tests/introspection/models.py
@@ -83,6 +83,7 @@ class Comment(models.Model):
 
 class CheckConstraintModel(models.Model):
     up_votes = models.PositiveIntegerField()
+    voting_number = models.PositiveIntegerField(unique=True)
 
     class Meta:
         required_db_features = {
diff --git a/tests/introspection/tests.py b/tests/introspection/tests.py
index 91b6ec732e..5e6fd3d741 100644
--- a/tests/introspection/tests.py
+++ b/tests/introspection/tests.py
@@ -268,9 +268,15 @@ class IntrospectionTests(TransactionTestCase):
             elif details['columns'] == ['up_votes'] and details['check']:
                 assertDetails(details, ['up_votes'], check=True)
                 field_constraints.add(name)
+            elif details['columns'] == ['voting_number'] and details['check']:
+                assertDetails(details, ['voting_number'], check=True)
+                field_constraints.add(name)
             elif details['columns'] == ['ref'] and details['unique']:
                 assertDetails(details, ['ref'], unique=True)
                 field_constraints.add(name)
+            elif details['columns'] == ['voting_number'] and details['unique']:
+                assertDetails(details, ['voting_number'], unique=True)
+                field_constraints.add(name)
             elif details['columns'] == ['article_id'] and details['index']:
                 assertDetails(details, ['article_id'], index=True)
                 field_constraints.add(name)