Fixed #17574 -- Implemented missing get_key_columns in PostgreSQL backend

1 files changed, 17 insertions, 0 deletions

diff --git a/django/db/backends/postgresql_psycopg2/introspection.py b/django/db/backends/postgresql_psycopg2/introspection.py
index 440fa44c4e..a71d107357 100644
--- a/django/db/backends/postgresql_psycopg2/introspection.py
+++ b/django/db/backends/postgresql_psycopg2/introspection.py
@@ -66,6 +66,23 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
             relations[row[0][0] - 1] = (row[1][0] - 1, row[2])
         return relations
 
+    def get_key_columns(self, cursor, table_name):
+        key_columns = []
+        cursor.execute("""
+            SELECT kcu.column_name, ccu.table_name AS referenced_table, ccu.column_name AS referenced_column
+            FROM information_schema.constraint_column_usage ccu
+            LEFT JOIN information_schema.key_column_usage kcu
+                ON ccu.constraint_catalog = kcu.constraint_catalog
+                    AND ccu.constraint_schema = kcu.constraint_schema
+                    AND ccu.constraint_name = kcu.constraint_name
+            LEFT JOIN information_schema.table_constraints tc
+                ON ccu.constraint_catalog = tc.constraint_catalog
+                    AND ccu.constraint_schema = tc.constraint_schema
+                    AND ccu.constraint_name = tc.constraint_name
+            WHERE kcu.table_name = %s AND tc.constraint_type = 'FOREIGN KEY'""" , [table_name])
+        key_columns.extend(cursor.fetchall())
+        return key_columns
+
     def get_indexes(self, cursor, table_name):
         # This query retrieves each index on the given table, including the
         # first associated field name