Improved 'django-admin inspectdb' so that it detects ForeignKey relationships -- PostgreSQL only

git-svn-id: http://code.djangoproject.com/svn/django/trunk@395 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/core/db/backends/postgresql.py

@@ -82,6 +82,27 @@ def get_table_list(cursor):
             AND pg_catalog.pg_table_is_visible(c.oid)""")
     return [row[0] for row in cursor.fetchall()]
 
+def get_relations(cursor, table_name):
+    """
+    Returns a dictionary of {field_index: (field_index_other_table, other_table)}
+    representing all relationships to the given table. Indexes are 0-based.
+    """
+    cursor.execute("""
+        SELECT con.conkey, con.confkey, c2.relname
+        FROM pg_constraint con, pg_class c1, pg_class c2
+        WHERE c1.oid = con.conrelid
+            AND c2.oid = con.confrelid
+            AND c1.relname = %s
+            AND con.contype = 'f'""", [table_name])
+    relations = {}
+    for row in cursor.fetchall():
+        try:
+            # row[0] and row[1] are like "{2}", so strip the curly braces.
+            relations[int(row[0][1:-1]) - 1] = (int(row[1][1:-1]) - 1, row[2])
+        except ValueError:
+            continue
+    return relations
+
 # Register these custom typecasts, because Django expects dates/times to be
 # in Python's native (standard-library) datetime/time format, whereas psycopg
 # use mx.DateTime by default.