205 lines
6.4 KiB
Python
205 lines
6.4 KiB
Python
# Copyright 2020 The Matrix.org Foundation C.I.C.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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from types import TracebackType
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from typing import (
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Any,
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Callable,
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Iterator,
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List,
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Mapping,
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Optional,
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Sequence,
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Tuple,
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Type,
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Union,
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)
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from typing_extensions import Protocol
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"""
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Some very basic protocol definitions for the DB-API2 classes specified in PEP-249
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"""
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SQLQueryParameters = Union[Sequence[Any], Mapping[str, Any]]
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class Cursor(Protocol):
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def execute(self, sql: str, parameters: SQLQueryParameters = ...) -> Any:
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...
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def executemany(self, sql: str, parameters: Sequence[SQLQueryParameters]) -> Any:
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...
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def fetchone(self) -> Optional[Tuple]:
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...
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def fetchmany(self, size: Optional[int] = ...) -> List[Tuple]:
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...
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def fetchall(self) -> List[Tuple]:
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...
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@property
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def description(
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self,
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) -> Optional[Sequence[Any]]:
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# At the time of writing, Synapse only assumes that `column[0]: str` for each
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# `column in description`. Since this is hard to express in the type system, and
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# as this is rarely used in Synapse, we deem `column: Any` good enough.
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...
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@property
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def rowcount(self) -> int:
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return 0
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def __iter__(self) -> Iterator[Tuple]:
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...
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def close(self) -> None:
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...
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class Connection(Protocol):
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def cursor(self) -> Cursor:
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...
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def close(self) -> None:
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...
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def commit(self) -> None:
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...
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def rollback(self) -> None:
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...
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def __enter__(self) -> "Connection":
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...
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def __exit__(
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self,
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exc_type: Optional[Type[BaseException]],
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exc_value: Optional[BaseException],
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traceback: Optional[TracebackType],
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) -> Optional[bool]:
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...
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class DBAPI2Module(Protocol):
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"""The module-level attributes that we use from PEP 249.
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This is NOT a comprehensive stub for the entire DBAPI2."""
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__name__: str
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# Exceptions. See https://peps.python.org/pep-0249/#exceptions
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# For our specific drivers:
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# - Python's sqlite3 module doesn't contains the same descriptions as the
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# DBAPI2 spec, see https://docs.python.org/3/library/sqlite3.html#exceptions
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# - Psycopg2 maps every Postgres error code onto a unique exception class which
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# extends from this hierarchy. See
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# https://docs.python.org/3/library/sqlite3.html?highlight=sqlite3#exceptions
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# https://www.postgresql.org/docs/current/errcodes-appendix.html#ERRCODES-TABLE
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#
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# Note: rather than
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# x: T
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# we write
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# @property
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# def x(self) -> T: ...
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# which expresses that the protocol attribute `x` is read-only. The mypy docs
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# https://mypy.readthedocs.io/en/latest/common_issues.html#covariant-subtyping-of-mutable-protocol-members-is-rejected
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# explain why this is necessary for safety. TL;DR: we shouldn't be able to write
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# to `x`, only read from it. See also https://github.com/python/mypy/issues/6002 .
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@property
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def Warning(self) -> Type[Exception]:
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...
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@property
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def Error(self) -> Type[Exception]:
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...
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# Errors are divided into `InterfaceError`s (something went wrong in the database
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# driver) and `DatabaseError`s (something went wrong in the database). These are
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# both subclasses of `Error`, but we can't currently express this in type
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# annotations due to https://github.com/python/mypy/issues/8397
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@property
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def InterfaceError(self) -> Type[Exception]:
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...
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@property
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def DatabaseError(self) -> Type[Exception]:
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...
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# Everything below is a subclass of `DatabaseError`.
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# Roughly: the database rejected a nonsensical value. Examples:
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# - An integer was too big for its data type.
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# - An invalid date time was provided.
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# - A string contained a null code point.
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@property
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def DataError(self) -> Type[Exception]:
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...
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# Roughly: something went wrong in the database, but it's not within the application
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# programmer's control. Examples:
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# - We failed to establish a connection to the database.
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# - The connection to the database was lost.
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# - A deadlock was detected.
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# - A serialisation failure occurred.
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# - The database ran out of resources, such as storage, memory, connections, etc.
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# - The database encountered an error from the operating system.
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@property
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def OperationalError(self) -> Type[Exception]:
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...
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# Roughly: we've given the database data which breaks a rule we asked it to enforce.
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# Examples:
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# - Stop, criminal scum! You violated the foreign key constraint
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# - Also check constraints, non-null constraints, etc.
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@property
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def IntegrityError(self) -> Type[Exception]:
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...
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# Roughly: something went wrong within the database server itself.
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@property
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def InternalError(self) -> Type[Exception]:
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...
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# Roughly: the application did something silly that needs to be fixed. Examples:
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# - We don't have permissions to do something.
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# - We tried to create a table with duplicate column names.
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# - We tried to use a reserved name.
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# - We referred to a column that doesn't exist.
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@property
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def ProgrammingError(self) -> Type[Exception]:
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...
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# Roughly: we've tried to do something that this database doesn't support.
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@property
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def NotSupportedError(self) -> Type[Exception]:
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...
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# We originally wrote
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# def connect(self, *args, **kwargs) -> Connection: ...
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# But mypy doesn't seem to like that because sqlite3.connect takes a mandatory
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# positional argument. We can't make that part of the signature though, because
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# psycopg2.connect doesn't have a mandatory positional argument. Instead, we use
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# the following slightly unusual workaround.
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@property
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def connect(self) -> Callable[..., Connection]:
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...
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__all__ = ["Cursor", "Connection", "DBAPI2Module"]
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