Merge remote-tracking branch 'upstream/master'

[nominatim.git] / nominatim / db / connection.py

diff --git a/nominatim/db/connection.py b/nominatim/db/connection.py
index 12f5f4e15f8c55b57c5fc68b93154942a9839c3c..c60bcfddb8af99faf3bc2ba4e7f7a48b7baf731f 100644 (file)
--- 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.
 """
@@ -8,8 +14,9 @@ import os
 import psycopg2
 import psycopg2.extensions
 import psycopg2.extras
+from psycopg2 import sql as pysql
 
-from ..errors import UsageError
+from nominatim.errors import UsageError
 
 LOG = logging.getLogger()
 
@@ -18,13 +25,24 @@ 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'))
 
         super().execute(query, args)
 
+
+    def execute_values(self, sql, argslist, template=None):
+        """ Wrapper for the psycopg2 convenience function to execute
+            SQL for a list of values.
+        """
+        LOG.debug("SQL execute_values(%s, %s)", sql, argslist)
+
+        psycopg2.extras.execute_values(self, sql, argslist, template=template)
+
+
     def scalar(self, sql, args=None):
         """ Execute query that returns a single value. The value is returned.
             If the query yields more than one row, a ValueError is raised.
@@ -37,6 +55,22 @@ class _Cursor(psycopg2.extras.DictCursor):
         return self.fetchone()[0]
 
 
+    def drop_table(self, name, if_exists=True, cascade=False):
+        """ Drop the table with the given name.
+            Set `if_exists` to False if a non-existant table should raise
+            an exception instead of just being ignored. If 'cascade' is set
+            to True then all dependent tables are deleted as well.
+        """
+        sql = 'DROP TABLE '
+        if if_exists:
+            sql += 'IF EXISTS '
+        sql += '{}'
+        if cascade:
+            sql += ' CASCADE'
+
+        self.execute(pysql.SQL(sql).format(pysql.Identifier(name)))
+
+
 class _Connection(psycopg2.extensions.connection):
     """ A connection that provides the specialised cursor by default and
         adds convenience functions for administrating the database.
@@ -57,6 +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
@@ -75,6 +120,16 @@ class _Connection(psycopg2.extensions.connection):
         return True
 
 
+    def drop_table(self, name, if_exists=True, cascade=False):
+        """ Drop the table with the given name.
+            Set `if_exists` to False if a non-existant table should raise
+            an exception instead of just being ignored.
+        """
+        with self.cursor() as cur:
+            cur.drop_table(name, if_exists, cascade)
+        self.commit()
+
+
     def server_version_tuple(self):
         """ Return the server version as a tuple of (major, minor).
             Converts correctly for pre-10 and post-10 PostgreSQL versions.
@@ -109,7 +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.