synapse/synapse/storage/engines/psycopg2.py

# 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.

import logging
from typing import Any, Mapping, Optional, NoReturn

import psycopg2.extensions

from synapse.storage.engines import PostgresEngine
from synapse.storage.engines._base import IsolationLevel


logger = logging.getLogger(__name__)


class Psycopg2Engine(
    PostgresEngine[psycopg2.extensions.connection, psycopg2.extensions.cursor, int]
):
    def __init__(self, database_config: Mapping[str, Any]):
        super().__init__(psycopg2, database_config)
        psycopg2.extensions.register_type(psycopg2.extensions.UNICODE)

        # Disables passing `bytes` to txn.execute, c.f.
        # https://github.com/matrix-org/synapse/issues/6186. If you do
        # actually want to use bytes than wrap it in `bytearray`.
        def _disable_bytes_adapter(_: bytes) -> NoReturn:
            raise Exception("Passing bytes to DB is disabled.")

        psycopg2.extensions.register_adapter(bytes, _disable_bytes_adapter)

        self.isolation_level_map = {
            IsolationLevel.READ_COMMITTED: psycopg2.extensions.ISOLATION_LEVEL_READ_COMMITTED,
            IsolationLevel.REPEATABLE_READ: psycopg2.extensions.ISOLATION_LEVEL_REPEATABLE_READ,
            IsolationLevel.SERIALIZABLE: psycopg2.extensions.ISOLATION_LEVEL_SERIALIZABLE,
        }
        self.default_isolation_level = (
            psycopg2.extensions.ISOLATION_LEVEL_REPEATABLE_READ
        )
        self.config = database_config

    def get_server_version(self, db_conn: psycopg2.extensions.connection) -> int:
        return db_conn.server_version

    def convert_param_style(self, sql: str) -> str:
        return sql.replace("?", "%s")

    def is_deadlock(self, error: Exception) -> bool:
        if isinstance(error, psycopg2.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 in_transaction(self, conn: psycopg2.extensions.connection) -> bool:
        return conn.status != psycopg2.extensions.STATUS_READY

    def attempt_to_set_autocommit(
        self, conn: psycopg2.extensions.connection, autocommit: bool
    ) -> None:
        return conn.set_session(autocommit=autocommit)

    def attempt_to_set_isolation_level(
        self, conn: psycopg2.extensions.connection, isolation_level: Optional[int]
    ) -> None:
        if isolation_level is None:
            isolation_level = self.default_isolation_level
        else:
            isolation_level = self.isolation_level_map[isolation_level]
        return conn.set_isolation_level(isolation_level)

    @staticmethod
    def executescript(cursor: psycopg2.extensions.cursor, script: str) -> None:
        """Execute a chunk of SQL containing multiple semicolon-delimited statements.

        Psycopg2 seems happy to do this in DBAPI2's `execute()` function.

        For consistency with SQLite, any ongoing transaction is committed before
        executing the script in its own transaction. The script transaction is
        left open and it is the responsibility of the caller to commit it.
        """
        cursor.execute(f"COMMIT; BEGIN TRANSACTION; {script}")