databases/databases/core.py at master · python-study-cxb/databases · GitHub

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import asyncio

import contextlib

import functools

import logging

import typing

from contextvars import ContextVar

from types import TracebackType

from urllib.parse import SplitResult, parse_qsl, unquote, urlsplit

from sqlalchemy import text

from sqlalchemy.sql import ClauseElement

from databases.importer import import_from_string

from databases.interfaces import DatabaseBackend, Record

try: # pragma: no cover

import click

# Extra log info for optional coloured terminal outputs.

LOG_EXTRA = {

"color_message": "Query: " + click.style("%s", bold=True) + " Args: %s"

}

CONNECT_EXTRA = {

"color_message": "Connected to database " + click.style("%s", bold=True)

}

DISCONNECT_EXTRA = {

"color_message": "Disconnected from database " + click.style("%s", bold=True)

}

except ImportError: # pragma: no cover

LOG_EXTRA = {}

CONNECT_EXTRA = {}

DISCONNECT_EXTRA = {}

logger = logging.getLogger("databases")

class Database:

SUPPORTED_BACKENDS = {

"postgresql": "databases.backends.postgres:PostgresBackend",

"postgresql+aiopg": "databases.backends.aiopg:AiopgBackend",

"postgres": "databases.backends.postgres:PostgresBackend",

"mysql": "databases.backends.mysql:MySQLBackend",

"mysql+asyncmy": "databases.backends.asyncmy:AsyncMyBackend",

"sqlite": "databases.backends.sqlite:SQLiteBackend",

}

def __init__(

self,

url: typing.Union[str, "DatabaseURL"],

force_rollback: bool = False,

**options: typing.Any,

self.url = DatabaseURL(url)

self.options = options

self.is_connected = False

self._force_rollback = force_rollback

backend_str = self._get_backend()

backend_cls = import_from_string(backend_str)

assert issubclass(backend_cls, DatabaseBackend)

self._backend = backend_cls(self.url, **self.options)

# Connections are stored as task-local state.

self._connection_context = ContextVar("connection_context") # type: ContextVar

# When `force_rollback=True` is used, we use a single global

# connection, within a transaction that always rolls back.

self._global_connection = None # type: typing.Optional[Connection]

self._global_transaction = None # type: typing.Optional[Transaction]

async def connect(self) -> None:

"""

Establish the connection pool.

"""

if self.is_connected:

logger.debug("Already connected, skipping connection")

return None

await self._backend.connect()

logger.info(

"Connected to database %s", self.url.obscure_password, extra=CONNECT_EXTRA

)

self.is_connected = True

if self._force_rollback:

assert self._global_connection is None

assert self._global_transaction is None

self._global_connection = Connection(self._backend)

self._global_transaction = self._global_connection.transaction(

force_rollback=True

)

await self._global_transaction.__aenter__()

async def disconnect(self) -> None:

"""

Close all connections in the connection pool.

"""

if not self.is_connected:

logger.debug("Already disconnected, skipping disconnection")

return None

if self._force_rollback:

assert self._global_connection is not None

assert self._global_transaction is not None

await self._global_transaction.__aexit__()

self._global_transaction = None

self._global_connection = None

else:

self._connection_context = ContextVar("connection_context")

await self._backend.disconnect()

logger.info(

"Disconnected from database %s",

self.url.obscure_password,

extra=DISCONNECT_EXTRA,

)

self.is_connected = False

async def __aenter__(self) -> "Database":

await self.connect()

return self

async def __aexit__(

self,

exc_type: typing.Type[BaseException] = None,

exc_value: BaseException = None,

traceback: TracebackType = None,

) -> None:

await self.disconnect()

async def fetch_all(

self, query: typing.Union[ClauseElement, str], values: dict = None

) -> typing.List[Record]:

async with self.connection() as connection:

return await connection.fetch_all(query, values)

async def fetch_one(

self, query: typing.Union[ClauseElement, str], values: dict = None

) -> typing.Optional[Record]:

async with self.connection() as connection:

return await connection.fetch_one(query, values)

async def fetch_val(

self,

query: typing.Union[ClauseElement, str],

values: dict = None,

column: typing.Any = 0,

) -> typing.Any:

async with self.connection() as connection:

return await connection.fetch_val(query, values, column=column)

async def execute(

self, query: typing.Union[ClauseElement, str], values: dict = None

) -> typing.Any:

async with self.connection() as connection:

return await connection.execute(query, values)

async def execute_many(

self, query: typing.Union[ClauseElement, str], values: list

) -> None:

async with self.connection() as connection:

return await connection.execute_many(query, values)

async def iterate(

self, query: typing.Union[ClauseElement, str], values: dict = None

) -> typing.AsyncGenerator[typing.Mapping, None]:

async with self.connection() as connection:

async for record in connection.iterate(query, values):

yield record

def connection(self) -> "Connection":

if self._global_connection is not None:

return self._global_connection

try:

return self._connection_context.get()

except LookupError:

connection = Connection(self._backend)

self._connection_context.set(connection)

return connection

def transaction(

self, *, force_rollback: bool = False, **kwargs: typing.Any

) -> "Transaction":

return Transaction(self.connection, force_rollback=force_rollback, **kwargs)

@contextlib.contextmanager

def force_rollback(self) -> typing.Iterator[None]:

initial = self._force_rollback

self._force_rollback = True

try:

yield

finally:

self._force_rollback = initial

def _get_backend(self) -> str:

return self.SUPPORTED_BACKENDS.get(

self.url.scheme, self.SUPPORTED_BACKENDS[self.url.dialect]

)

class Connection:

def __init__(self, backend: DatabaseBackend) -> None:

self._backend = backend

self._connection_lock = asyncio.Lock()

self._connection = self._backend.connection()

self._connection_counter = 0

self._transaction_lock = asyncio.Lock()

self._transaction_stack = [] # type: typing.List[Transaction]

self._query_lock = asyncio.Lock()

async def __aenter__(self) -> "Connection":

async with self._connection_lock:

self._connection_counter += 1

try:

if self._connection_counter == 1:

await self._connection.acquire()

except BaseException as e:

self._connection_counter -= 1

raise e

return self

async def __aexit__(

self,

exc_type: typing.Type[BaseException] = None,

exc_value: BaseException = None,

traceback: TracebackType = None,

) -> None:

async with self._connection_lock:

assert self._connection is not None

self._connection_counter -= 1

if self._connection_counter == 0:

await self._connection.release()

async def fetch_all(

self, query: typing.Union[ClauseElement, str], values: dict = None

) -> typing.List[Record]:

built_query = self._build_query(query, values)

async with self._query_lock:

return await self._connection.fetch_all(built_query)

async def fetch_one(

self, query: typing.Union[ClauseElement, str], values: dict = None

) -> typing.Optional[Record]:

built_query = self._build_query(query, values)

async with self._query_lock:

return await self._connection.fetch_one(built_query)

async def fetch_val(

self,

query: typing.Union[ClauseElement, str],

values: dict = None,

column: typing.Any = 0,

) -> typing.Any:

built_query = self._build_query(query, values)

async with self._query_lock:

return await self._connection.fetch_val(built_query, column)

async def execute(

self, query: typing.Union[ClauseElement, str], values: dict = None

) -> typing.Any:

built_query = self._build_query(query, values)

async with self._query_lock:

return await self._connection.execute(built_query)

async def execute_many(

self, query: typing.Union[ClauseElement, str], values: list

) -> None:

queries = [self._build_query(query, values_set) for values_set in values]

async with self._query_lock:

await self._connection.execute_many(queries)

async def iterate(

self, query: typing.Union[ClauseElement, str], values: dict = None

) -> typing.AsyncGenerator[typing.Any, None]:

built_query = self._build_query(query, values)

async with self.transaction():

async with self._query_lock:

async for record in self._connection.iterate(built_query):

yield record

def transaction(

self, *, force_rollback: bool = False, **kwargs: typing.Any

) -> "Transaction":

def connection_callable() -> Connection:

return self

return Transaction(connection_callable, force_rollback, **kwargs)

@property

def raw_connection(self) -> typing.Any:

return self._connection.raw_connection

@staticmethod

def _build_query(

query: typing.Union[ClauseElement, str], values: dict = None

) -> ClauseElement:

if isinstance(query, str):

query = text(query)

return query.bindparams(**values) if values is not None else query

elif values:

return query.values(**values)

return query

_CallableType = typing.TypeVar("_CallableType", bound=typing.Callable)

class Transaction:

def __init__(

self,

connection_callable: typing.Callable[[], Connection],

force_rollback: bool,

**kwargs: typing.Any,

) -> None:

self._connection_callable = connection_callable

self._force_rollback = force_rollback

self._extra_options = kwargs

async def __aenter__(self) -> "Transaction":

"""

Called when entering `async with database.transaction()`

"""

await self.start()

return self

async def __aexit__(

self,

exc_type: typing.Type[BaseException] = None,

exc_value: BaseException = None,

traceback: TracebackType = None,

) -> None:

"""

Called when exiting `async with database.transaction()`

"""

if exc_type is not None or self._force_rollback:

await self.rollback()

else:

await self.commit()

def __await__(self) -> typing.Generator[None, None, "Transaction"]:

"""

Called if using the low-level `transaction = await database.transaction()`

"""

return self.start().__await__()

def __call__(self, func: _CallableType) -> _CallableType:

"""

Called if using `@database.transaction()` as a decorator.

"""

@functools.wraps(func)

async def wrapper(*args: typing.Any, **kwargs: typing.Any) -> typing.Any:

async with self:

return await func(*args, **kwargs)

return wrapper # type: ignore

async def start(self) -> "Transaction":

self._connection = self._connection_callable()

self._transaction = self._connection._connection.transaction()

async with self._connection._transaction_lock:

is_root = not self._connection._transaction_stack

await self._connection.__aenter__()

await self._transaction.start(

is_root=is_root, extra_options=self._extra_options

)

self._connection._transaction_stack.append(self)

return self

async def commit(self) -> None:

async with self._connection._transaction_lock:

assert self._connection._transaction_stack[-1] is self

self._connection._transaction_stack.pop()

await self._transaction.commit()

await self._connection.__aexit__()

async def rollback(self) -> None:

async with self._connection._transaction_lock:

assert self._connection._transaction_stack[-1] is self

self._connection._transaction_stack.pop()

await self._transaction.rollback()

await self._connection.__aexit__()

class _EmptyNetloc(str):

def __bool__(self) -> bool:

return True

class DatabaseURL:

def __init__(self, url: typing.Union[str, "DatabaseURL"]):

if isinstance(url, DatabaseURL):

self._url: str = url._url

elif isinstance(url, str):

self._url = url

else:

raise TypeError(

f"Invalid type for DatabaseURL. Expected str or DatabaseURL, got {type(url)}"

)

@property

def components(self) -> SplitResult:

if not hasattr(self, "_components"):

self._components = urlsplit(self._url)

return self._components

@property

def scheme(self) -> str:

return self.components.scheme

@property

def dialect(self) -> str:

return self.components.scheme.split("+")[0]

@property

def driver(self) -> str:

if "+" not in self.components.scheme:

return ""

return self.components.scheme.split("+", 1)[1]

@property

def userinfo(self) -> typing.Optional[bytes]:

if self.components.username:

info = self.components.username

if self.components.password:

info += ":" + self.components.password

return info.encode("utf-8")

return None

@property

def username(self) -> typing.Optional[str]:

if self.components.username is None:

return None

return unquote(self.components.username)

@property

def password(self) -> typing.Optional[str]:

if self.components.password is None:

return None

return unquote(self.components.password)

@property

def hostname(self) -> typing.Optional[str]:

return (

self.components.hostname

or self.options.get("host")

or self.options.get("unix_sock")

)

@property

def port(self) -> typing.Optional[int]:

return self.components.port

@property

def netloc(self) -> typing.Optional[str]:

return self.components.netloc

@property

def database(self) -> str:

path = self.components.path

if path.startswith("/"):

path = path[1:]

return unquote(path)

@property

def options(self) -> dict:

if not hasattr(self, "_options"):

self._options = dict(parse_qsl(self.components.query))

return self._options

def replace(self, **kwargs: typing.Any) -> "DatabaseURL":

if (

"username" in kwargs

or "password" in kwargs

or "hostname" in kwargs

or "port" in kwargs

hostname = kwargs.pop("hostname", self.hostname)

port = kwargs.pop("port", self.port)

username = kwargs.pop("username", self.components.username)

password = kwargs.pop("password", self.components.password)

netloc = hostname

if port is not None:

netloc += f":{port}"

if username is not None:

userpass = username

if password is not None:

userpass += f":{password}"

netloc = f"{userpass}@{netloc}"

kwargs["netloc"] = netloc

if "database" in kwargs:

kwargs["path"] = "/" + kwargs.pop("database")

if "dialect" in kwargs or "driver" in kwargs:

dialect = kwargs.pop("dialect", self.dialect)

driver = kwargs.pop("driver", self.driver)

kwargs["scheme"] = f"{dialect}+{driver}" if driver else dialect

if not kwargs.get("netloc", self.netloc):

# Using an empty string that evaluates as True means we end up

# with URLs like `sqlite:///database` instead of `sqlite:/database`

kwargs["netloc"] = _EmptyNetloc()

components = self.components._replace(**kwargs)

return self.__class__(components.geturl())

@property

def obscure_password(self) -> str:

if self.password:

return self.replace(password="********")._url

return self._url

def __str__(self) -> str:

return self._url

def __repr__(self) -> str:

return f"{self.__class__.__name__}({repr(self.obscure_password)})"

def __eq__(self, other: typing.Any) -> bool:

return str(self) == str(other)

databases/databases/core.py at master · python-study-cxb/databases · GitHub

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