"""
Specialised connection and cursor functions.
"""
+import contextlib
import logging
+import os
import psycopg2
import psycopg2.extensions
import psycopg2.extras
+from psycopg2 import sql as pysql
+
+from nominatim.errors import UsageError
+
+LOG = logging.getLogger()
class _Cursor(psycopg2.extras.DictCursor):
""" A cursor returning dict-like objects and providing specialised
def execute(self, query, args=None): # pylint: disable=W0221
""" Query execution that logs the SQL query when debugging is enabled.
"""
- logger = logging.getLogger()
- logger.debug(self.mogrify(query, args).decode('utf-8'))
+ 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.
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.
"""
return super().cursor(cursor_factory=cursor_factory, **kwargs)
+
def table_exists(self, table):
""" Check that a table with the given name exists in the database.
"""
with self.cursor() as cur:
num = cur.scalar("""SELECT count(*) FROM pg_tables
- WHERE tablename = %s""", (table, ))
+ WHERE tablename = %s and schemaname = 'public'""", (table, ))
return num == 1
+
+ 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
+ table.
+ """
+ with self.cursor() as cur:
+ cur.execute("""SELECT tablename FROM pg_indexes
+ WHERE indexname = %s and schemaname = 'public'""", (index, ))
+ if cur.rowcount == 0:
+ return False
+
+ if table is not None:
+ row = cur.fetchone()
+ return row[0] == table
+
+ 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.
"""
version = self.server_version
if version < 100000:
- return (version / 10000, (version % 10000) / 100)
+ return (int(version / 10000), (version % 10000) / 100)
+
+ return (int(version / 10000), version % 10000)
+
+
+ def postgis_version_tuple(self):
+ """ Return the postgis version installed in the database as a
+ tuple of (major, minor). Assumes that the PostGIS extension
+ has been installed already.
+ """
+ with self.cursor() as cur:
+ version = cur.scalar('SELECT postgis_lib_version()')
+
+ return tuple((int(x) for x in version.split('.')[:2]))
- return (version / 10000, version % 10000)
def connect(dsn):
""" Open a connection to the database using the specialised connection
- factory.
+ factory. The returned object may be used in conjunction with 'with'.
+ When used outside a context manager, use the `connection` attribute
+ to get the connection.
"""
- return psycopg2.connect(dsn, connection_factory=_Connection)
+ try:
+ conn = psycopg2.connect(dsn, connection_factory=_Connection)
+ ctxmgr = contextlib.closing(conn)
+ ctxmgr.connection = conn
+ return ctxmgr
+ except psycopg2.OperationalError as err:
+ raise UsageError("Cannot connect to database: {}".format(err)) from err
+
+
+# Translation from PG connection string parameters to PG environment variables.
+# Derived from https://www.postgresql.org/docs/current/libpq-envars.html.
+_PG_CONNECTION_STRINGS = {
+ 'host': 'PGHOST',
+ 'hostaddr': 'PGHOSTADDR',
+ 'port': 'PGPORT',
+ 'dbname': 'PGDATABASE',
+ 'user': 'PGUSER',
+ 'password': 'PGPASSWORD',
+ 'passfile': 'PGPASSFILE',
+ 'channel_binding': 'PGCHANNELBINDING',
+ 'service': 'PGSERVICE',
+ 'options': 'PGOPTIONS',
+ 'application_name': 'PGAPPNAME',
+ 'sslmode': 'PGSSLMODE',
+ 'requiressl': 'PGREQUIRESSL',
+ 'sslcompression': 'PGSSLCOMPRESSION',
+ 'sslcert': 'PGSSLCERT',
+ 'sslkey': 'PGSSLKEY',
+ 'sslrootcert': 'PGSSLROOTCERT',
+ 'sslcrl': 'PGSSLCRL',
+ 'requirepeer': 'PGREQUIREPEER',
+ 'ssl_min_protocol_version': 'PGSSLMINPROTOCOLVERSION',
+ 'ssl_max_protocol_version': 'PGSSLMAXPROTOCOLVERSION',
+ 'gssencmode': 'PGGSSENCMODE',
+ 'krbsrvname': 'PGKRBSRVNAME',
+ 'gsslib': 'PGGSSLIB',
+ 'connect_timeout': 'PGCONNECT_TIMEOUT',
+ 'target_session_attrs': 'PGTARGETSESSIONATTRS',
+}
+
+
+def get_pg_env(dsn, base_env=None):
+ """ Return a copy of `base_env` with the environment variables for
+ PostgresSQL set up from the given database connection string.
+ If `base_env` is None, then the OS environment is used as a base
+ environment.
+ """
+ env = dict(base_env if base_env is not None else os.environ)
+
+ for param, value in psycopg2.extensions.parse_dsn(dsn).items():
+ if param in _PG_CONNECTION_STRINGS:
+ env[_PG_CONNECTION_STRINGS[param]] = value
+ else:
+ LOG.error("Unknown connection parameter '%s' ignored.", param)
+
+ return env
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