X-Git-Url: https://git.openstreetmap.org./nominatim.git/blobdiff_plain/6f6681ce67dc1a4c9cfe52cf61bc3ecfbaf2f5f1..3bcd32ca2006cb2184f290e18f4e054f8aca8bf4:/nominatim/db/connection.py?ds=sidebyside

diff --git a/nominatim/db/connection.py b/nominatim/db/connection.py
index 1319ac16..c60bcfdd 100644
--- a/nominatim/db/connection.py
+++ b/nominatim/db/connection.py
@@ -1,3 +1,9 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# This file is part of Nominatim. (https://nominatim.org)
+#
+# Copyright (C) 2022 by the Nominatim developer community.
+# For a full list of authors see the git log.
 """
 Specialised connection and cursor functions.
 """
@@ -19,7 +25,8 @@ class _Cursor(psycopg2.extras.DictCursor):
         execution functions.
     """
 
-    def execute(self, query, args=None): # pylint: disable=W0221
+    # pylint: disable=arguments-renamed,arguments-differ
+    def execute(self, query, args=None):
         """ Query execution that logs the SQL query when debugging is enabled.
         """
         LOG.debug(self.mogrify(query, args).decode('utf-8'))
@@ -84,6 +91,17 @@ class _Connection(psycopg2.extensions.connection):
             return num == 1
 
 
+    def table_has_column(self, table, column):
+        """ Check if the table 'table' exists and has a column with name 'column'.
+        """
+        with self.cursor() as cur:
+            has_column = cur.scalar("""SELECT count(*) FROM information_schema.columns
+                                       WHERE table_name = %s
+                                             and column_name = %s""",
+                                    (table, column))
+            return has_column > 0
+
+
     def index_exists(self, index, table=None):
         """ Check that an index with the given name exists in the database.
             If table is not None then the index must relate to the given
@@ -146,7 +164,7 @@ def connect(dsn):
         ctxmgr.connection = conn
         return ctxmgr
     except psycopg2.OperationalError as err:
-        raise UsageError("Cannot connect to database: {}".format(err)) from err
+        raise UsageError(f"Cannot connect to database: {err}") from err
 
 
 # Translation from PG connection string parameters to PG environment variables.