Source code for aiopg.sa.engine

import asyncio
import json

import aiopg

from ..connection import TIMEOUT
from ..utils import _ContextManager, _PoolContextManager, get_running_loop
from .connection import SAConnection

try:
    from sqlalchemy.dialects.postgresql.psycopg2 import (
        PGCompiler_psycopg2,
        PGDialect_psycopg2,
    )
except ImportError:  # pragma: no cover
    raise ImportError('aiopg.sa requires sqlalchemy')


class APGCompiler_psycopg2(PGCompiler_psycopg2):
    def construct_params(self, params=None, _group_number=None, _check=True):
        pd = super().construct_params(params, _group_number, _check)

        for column in self.prefetch:
            pd[column.key] = self._exec_default(column.default)

        return pd

    def _exec_default(self, default):
        if default.is_callable:
            return default.arg(self.dialect)
        else:
            return default.arg


def get_dialect(json_serializer=json.dumps, json_deserializer=lambda x: x):
    dialect = PGDialect_psycopg2(json_serializer=json_serializer,
                                 json_deserializer=json_deserializer)

    dialect.statement_compiler = APGCompiler_psycopg2
    dialect.implicit_returning = True
    dialect.supports_native_enum = True
    dialect.supports_smallserial = True  # 9.2+
    dialect._backslash_escapes = False
    dialect.supports_sane_multi_rowcount = True  # psycopg 2.0.9+
    dialect._has_native_hstore = True

    return dialect


_dialect = get_dialect()


[docs]def create_engine(dsn=None, *, minsize=1, maxsize=10, dialect=_dialect, timeout=TIMEOUT, pool_recycle=-1, **kwargs): """A coroutine for Engine creation. Returns Engine instance with embedded connection pool. The pool has *minsize* opened connections to PostgreSQL server. """ coro = _create_engine(dsn=dsn, minsize=minsize, maxsize=maxsize, dialect=dialect, timeout=timeout, pool_recycle=pool_recycle, **kwargs) return _EngineContextManager(coro)
async def _create_engine(dsn=None, *, minsize=1, maxsize=10, dialect=_dialect, timeout=TIMEOUT, pool_recycle=-1, **kwargs): pool = await aiopg.create_pool( dsn, minsize=minsize, maxsize=maxsize, timeout=timeout, pool_recycle=pool_recycle, **kwargs ) conn = await pool.acquire() try: real_dsn = conn.dsn return Engine(dialect, pool, real_dsn) finally: await pool.release(conn)
[docs]class Engine: """Connects a aiopg.Pool and sqlalchemy.engine.interfaces.Dialect together to provide a source of database connectivity and behavior. An Engine object is instantiated publicly using the create_engine coroutine. """ __slots__ = ("_dialect", "_pool", "_dsn", "_loop") def __init__(self, dialect, pool, dsn): self._dialect = dialect self._pool = pool self._dsn = dsn self._loop = get_running_loop() @property def dialect(self): """An dialect for engine.""" return self._dialect @property def name(self): """A name of the dialect.""" return self._dialect.name @property def driver(self): """A driver of the dialect.""" return self._dialect.driver @property def dsn(self): """DSN connection info""" return self._dsn @property def timeout(self): return self._pool.timeout @property def minsize(self): return self._pool.minsize @property def maxsize(self): return self._pool.maxsize @property def size(self): return self._pool.size @property def freesize(self): return self._pool.freesize @property def closed(self): return self._pool.closed
[docs] def close(self): """Close engine. Mark all engine connections to be closed on getting back to pool. Closed engine doesn't allow to acquire new connections. """ self._pool.close()
[docs] def terminate(self): """Terminate engine. Terminate engine pool with instantly closing all acquired connections also. """ self._pool.terminate()
[docs] async def wait_closed(self): """Wait for closing all engine's connections.""" await self._pool.wait_closed()
[docs] def acquire(self): """Get a connection from pool.""" coro = self._acquire() return _EngineAcquireContextManager(coro)
async def _acquire(self): raw = await self._pool.acquire() conn = SAConnection(raw, self) return conn
[docs] def release(self, conn): fut = self._pool.release(conn.connection) return fut
def __enter__(self): raise RuntimeError( '"await" should be used as context manager expression') def __exit__(self, *args): # This must exist because __enter__ exists, even though that # always raises; that's how the with-statement works. pass # pragma: nocover def __await__(self): # This is not a coroutine. It is meant to enable the idiom: # # with (await engine) as conn: # <block> # # as an alternative to: # # conn = await engine.acquire() # try: # <block> # finally: # engine.release(conn) conn = yield from self._acquire().__await__() return _ConnectionContextManager(conn, self._loop) async def __aenter__(self): return self async def __aexit__(self, exc_type, exc_val, exc_tb): self.close() await self.wait_closed()
_EngineContextManager = _PoolContextManager _EngineAcquireContextManager = _ContextManager class _ConnectionContextManager: """Context manager. This enables the following idiom for acquiring and releasing a connection around a block: async with engine as conn: cur = await conn.cursor() while failing loudly when accidentally using: with engine: <block> """ __slots__ = ('_conn', '_loop') def __init__(self, conn: SAConnection, loop: asyncio.AbstractEventLoop): self._conn = conn self._loop = loop def __enter__(self): return self._conn def __exit__(self, *args): asyncio.ensure_future(self._conn.close(), loop=self._loop) self._conn = None