Fixed #29613 -- Fixed --keepdb on PostgreSQL if the database exists and the user can't create databases.

Regression in e776dd2db677d58dcb50aea20d3bb191537df25b.

Thanks Tim Graham for the review.

1 files changed, 9 insertions, 0 deletions

diff --git a/django/db/backends/postgresql/creation.py b/django/db/backends/postgresql/creation.py
index 8b6c4eff19..01e3b5d10a 100644
--- a/django/db/backends/postgresql/creation.py
+++ b/django/db/backends/postgresql/creation.py
@@ -3,6 +3,7 @@ import sys
 from psycopg2 import errorcodes
 
 from django.db.backends.base.creation import BaseDatabaseCreation
+from django.db.backends.utils import strip_quotes
 
 
 class DatabaseCreation(BaseDatabaseCreation):
@@ -28,8 +29,16 @@ class DatabaseCreation(BaseDatabaseCreation):
             template=test_settings.get('TEMPLATE'),
         )
 
+    def _database_exists(self, cursor, database_name):
+        cursor.execute('SELECT 1 FROM pg_catalog.pg_database WHERE datname = %s', [strip_quotes(database_name)])
+        return cursor.fetchone() is not None
+
     def _execute_create_test_db(self, cursor, parameters, keepdb=False):
         try:
+            if keepdb and self._database_exists(cursor, parameters['dbname']):
+                # If the database should be kept and it already exists, don't
+                # try to create a new one.
+                return
             super()._execute_create_test_db(cursor, parameters, keepdb)
         except Exception as e:
             if getattr(e.__cause__, 'pgcode', '') != errorcodes.DUPLICATE_DATABASE: