1# Copyright 2015, 2016 OpenMarket Ltd
2#
3# Licensed under the Apache License, Version 2.0 (the "License");
4# you may not use this file except in compliance with the License.
5# You may obtain a copy of the License at
6#
7#     http://www.apache.org/licenses/LICENSE-2.0
8#
9# Unless required by applicable law or agreed to in writing, software
10# distributed under the License is distributed on an "AS IS" BASIS,
11# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12# See the License for the specific language governing permissions and
13# limitations under the License.
14
15import logging
16
17from synapse.storage.engines._base import BaseDatabaseEngine, IncorrectDatabaseSetup
18from synapse.storage.types import Connection
19
20logger = logging.getLogger(__name__)
21
22
23class PostgresEngine(BaseDatabaseEngine):
24    def __init__(self, database_module, database_config):
25        super().__init__(database_module, database_config)
26        self.module.extensions.register_type(self.module.extensions.UNICODE)
27
28        # Disables passing `bytes` to txn.execute, c.f. #6186. If you do
29        # actually want to use bytes than wrap it in `bytearray`.
30        def _disable_bytes_adapter(_):
31            raise Exception("Passing bytes to DB is disabled.")
32
33        self.module.extensions.register_adapter(bytes, _disable_bytes_adapter)
34        self.synchronous_commit = database_config.get("synchronous_commit", True)
35        self._version = None  # unknown as yet
36
37    @property
38    def single_threaded(self) -> bool:
39        return False
40
41    def check_database(self, db_conn, allow_outdated_version: bool = False):
42        # Get the version of PostgreSQL that we're using. As per the psycopg2
43        # docs: The number is formed by converting the major, minor, and
44        # revision numbers into two-decimal-digit numbers and appending them
45        # together. For example, version 8.1.5 will be returned as 80105
46        self._version = db_conn.server_version
47
48        # Are we on a supported PostgreSQL version?
49        if not allow_outdated_version and self._version < 90600:
50            raise RuntimeError("Synapse requires PostgreSQL 9.6 or above.")
51
52        with db_conn.cursor() as txn:
53            txn.execute("SHOW SERVER_ENCODING")
54            rows = txn.fetchall()
55            if rows and rows[0][0] != "UTF8":
56                raise IncorrectDatabaseSetup(
57                    "Database has incorrect encoding: '%s' instead of 'UTF8'\n"
58                    "See docs/postgres.md for more information." % (rows[0][0],)
59                )
60
61            txn.execute(
62                "SELECT datcollate, datctype FROM pg_database WHERE datname = current_database()"
63            )
64            collation, ctype = txn.fetchone()
65            if collation != "C":
66                logger.warning(
67                    "Database has incorrect collation of %r. Should be 'C'\n"
68                    "See docs/postgres.md for more information.",
69                    collation,
70                )
71
72            if ctype != "C":
73                logger.warning(
74                    "Database has incorrect ctype of %r. Should be 'C'\n"
75                    "See docs/postgres.md for more information.",
76                    ctype,
77                )
78
79    def check_new_database(self, txn):
80        """Gets called when setting up a brand new database. This allows us to
81        apply stricter checks on new databases versus existing database.
82        """
83
84        txn.execute(
85            "SELECT datcollate, datctype FROM pg_database WHERE datname = current_database()"
86        )
87        collation, ctype = txn.fetchone()
88
89        errors = []
90
91        if collation != "C":
92            errors.append("    - 'COLLATE' is set to %r. Should be 'C'" % (collation,))
93
94        if ctype != "C":
95            errors.append("    - 'CTYPE' is set to %r. Should be 'C'" % (ctype,))
96
97        if errors:
98            raise IncorrectDatabaseSetup(
99                "Database is incorrectly configured:\n\n%s\n\n"
100                "See docs/postgres.md for more information." % ("\n".join(errors))
101            )
102
103    def convert_param_style(self, sql):
104        return sql.replace("?", "%s")
105
106    def on_new_connection(self, db_conn):
107        db_conn.set_isolation_level(
108            self.module.extensions.ISOLATION_LEVEL_REPEATABLE_READ
109        )
110
111        # Set the bytea output to escape, vs the default of hex
112        cursor = db_conn.cursor()
113        cursor.execute("SET bytea_output TO escape")
114
115        # Asynchronous commit, don't wait for the server to call fsync before
116        # ending the transaction.
117        # https://www.postgresql.org/docs/current/static/wal-async-commit.html
118        if not self.synchronous_commit:
119            cursor.execute("SET synchronous_commit TO OFF")
120
121        cursor.close()
122        db_conn.commit()
123
124    @property
125    def can_native_upsert(self):
126        """
127        Can we use native UPSERTs?
128        """
129        return True
130
131    @property
132    def supports_using_any_list(self):
133        """Do we support using `a = ANY(?)` and passing a list"""
134        return True
135
136    @property
137    def supports_returning(self) -> bool:
138        """Do we support the `RETURNING` clause in insert/update/delete?"""
139        return True
140
141    def is_deadlock(self, error):
142        if isinstance(error, self.module.DatabaseError):
143            # https://www.postgresql.org/docs/current/static/errcodes-appendix.html
144            # "40001" serialization_failure
145            # "40P01" deadlock_detected
146            return error.pgcode in ["40001", "40P01"]
147        return False
148
149    def is_connection_closed(self, conn):
150        return bool(conn.closed)
151
152    def lock_table(self, txn, table):
153        txn.execute("LOCK TABLE %s in EXCLUSIVE MODE" % (table,))
154
155    @property
156    def server_version(self):
157        """Returns a string giving the server version. For example: '8.1.5'
158
159        Returns:
160            string
161        """
162        # note that this is a bit of a hack because it relies on check_database
163        # having been called. Still, that should be a safe bet here.
164        numver = self._version
165        assert numver is not None
166
167        # https://www.postgresql.org/docs/current/libpq-status.html#LIBPQ-PQSERVERVERSION
168        if numver >= 100000:
169            return "%i.%i" % (numver / 10000, numver % 10000)
170        else:
171            return "%i.%i.%i" % (numver / 10000, (numver % 10000) / 100, numver % 100)
172
173    def in_transaction(self, conn: Connection) -> bool:
174        return conn.status != self.module.extensions.STATUS_READY  # type: ignore
175
176    def attempt_to_set_autocommit(self, conn: Connection, autocommit: bool):
177        return conn.set_session(autocommit=autocommit)  # type: ignore
178