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# -*- coding: utf-8 -*-
# Copyright 2015, 2016 OpenMarket Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from ._base import IncorrectDatabaseSetup
class PostgresEngine(object):
single_threaded = False
def __init__(self, database_module, database_config):
self.module = database_module
self.module.extensions.register_type(self.module.extensions.UNICODE)
self.synchronous_commit = database_config.get("synchronous_commit", True)
self._version = None # unknown as yet
def check_database(self, txn):
txn.execute("SHOW SERVER_ENCODING")
rows = txn.fetchall()
if rows and rows[0][0] != "UTF8":
raise IncorrectDatabaseSetup(
"Database has incorrect encoding: '%s' instead of 'UTF8'\n"
"See docs/postgres.rst for more information." % (rows[0][0],)
)
def convert_param_style(self, sql):
return sql.replace("?", "%s")
def on_new_connection(self, db_conn):
# Get the version of PostgreSQL that we're using. As per the psycopg2
# docs: The number is formed by converting the major, minor, and
# revision numbers into two-decimal-digit numbers and appending them
# together. For example, version 8.1.5 will be returned as 80105
self._version = db_conn.server_version
db_conn.set_isolation_level(
self.module.extensions.ISOLATION_LEVEL_REPEATABLE_READ
)
# Set the bytea output to escape, vs the default of hex
cursor = db_conn.cursor()
cursor.execute("SET bytea_output TO escape")
# Asynchronous commit, don't wait for the server to call fsync before
# ending the transaction.
# https://www.postgresql.org/docs/current/static/wal-async-commit.html
if not self.synchronous_commit:
cursor.execute("SET synchronous_commit TO OFF")
cursor.close()
@property
def can_native_upsert(self):
"""
Can we use native UPSERTs? This requires PostgreSQL 9.5+.
"""
return self._version >= 90500
def is_deadlock(self, error):
if isinstance(error, self.module.DatabaseError):
# https://www.postgresql.org/docs/current/static/errcodes-appendix.html
# "40001" serialization_failure
# "40P01" deadlock_detected
return error.pgcode in ["40001", "40P01"]
return False
def is_connection_closed(self, conn):
return bool(conn.closed)
def lock_table(self, txn, table):
txn.execute("LOCK TABLE %s in EXCLUSIVE MODE" % (table,))
def get_next_state_group_id(self, txn):
"""Returns an int that can be used as a new state_group ID
"""
txn.execute("SELECT nextval('state_group_id_seq')")
return txn.fetchone()[0]
@property
def server_version(self):
"""Returns a string giving the server version. For example: '8.1.5'
Returns:
string
"""
# note that this is a bit of a hack because it relies on on_new_connection
# having been called at least once. Still, that should be a safe bet here.
numver = self._version
assert numver is not None
# https://www.postgresql.org/docs/current/libpq-status.html#LIBPQ-PQSERVERVERSION
if numver >= 100000:
return "%i.%i" % (numver / 10000, numver % 10000)
else:
return "%i.%i.%i" % (numver / 10000, (numver % 10000) / 100, numver % 100)
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