Simplified introspection of constraints on MySQL.

Co-authored-by: Mariusz Felisiak <felisiak.mariusz@gmail.com>

1 files changed, 11 insertions, 20 deletions

diff --git a/django/db/backends/mysql/introspection.py b/django/db/backends/mysql/introspection.py
index 649df5c6d9..346765e30a 100644
--- a/django/db/backends/mysql/introspection.py
+++ b/django/db/backends/mysql/introspection.py
@@ -211,20 +211,26 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
         # Get the actual constraint names and columns
         name_query = """
             SELECT kc.`constraint_name`, kc.`column_name`,
-                kc.`referenced_table_name`, kc.`referenced_column_name`
-            FROM information_schema.key_column_usage AS kc
+                kc.`referenced_table_name`, kc.`referenced_column_name`,
+                c.`constraint_type`
+            FROM
+                information_schema.key_column_usage AS kc,
+                information_schema.table_constraints AS c
             WHERE
                 kc.table_schema = DATABASE() AND
+                c.table_schema = kc.table_schema AND
+                c.constraint_name = kc.constraint_name AND
+                c.constraint_type != 'CHECK' AND
                 kc.table_name = %s
             ORDER BY kc.`ordinal_position`
         """
         cursor.execute(name_query, [table_name])
-        for constraint, column, ref_table, ref_column in cursor.fetchall():
+        for constraint, column, ref_table, ref_column, kind in cursor.fetchall():
             if constraint not in constraints:
                 constraints[constraint] = {
                     'columns': OrderedSet(),
-                    'primary_key': False,
-                    'unique': False,
+                    'primary_key': kind == 'PRIMARY KEY',
+                    'unique': kind in {'PRIMARY KEY', 'UNIQUE'},
                     'index': False,
                     'check': False,
                     'foreign_key': (ref_table, ref_column) if ref_column else None,
@@ -232,21 +238,6 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
                 if self.connection.features.supports_index_column_ordering:
                     constraints[constraint]['orders'] = []
             constraints[constraint]['columns'].add(column)
-        # Now get the constraint types
-        type_query = """
-            SELECT c.constraint_name, c.constraint_type
-            FROM information_schema.table_constraints AS c
-            WHERE
-                c.table_schema = DATABASE() AND
-                c.table_name = %s
-        """
-        cursor.execute(type_query, [table_name])
-        for constraint, kind in cursor.fetchall():
-            if kind.lower() == "primary key":
-                constraints[constraint]['primary_key'] = True
-                constraints[constraint]['unique'] = True
-            elif kind.lower() == "unique":
-                constraints[constraint]['unique'] = True
         # Add check constraints.
         if self.connection.features.can_introspect_check_constraints:
             unnamed_constraints_index = 0