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Query locking #108

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Jun 25, 2019
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24 changes: 17 additions & 7 deletions databases/core.py
Original file line number Diff line number Diff line change
Expand Up @@ -160,6 +160,8 @@ def __init__(self, backend: DatabaseBackend) -> None:
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
Expand All @@ -182,38 +184,46 @@ async def __aexit__(
async def fetch_all(
self, query: typing.Union[ClauseElement, str], values: dict = None
) -> typing.List[typing.Mapping]:
return await self._connection.fetch_all(self._build_query(query, values))
async with self._query_lock:
return await self._connection.fetch_all(self._build_query(query, values))

async def fetch_one(
self, query: typing.Union[ClauseElement, str], values: dict = None
) -> typing.Optional[typing.Mapping]:
return await self._connection.fetch_one(self._build_query(query, values))
async with self._query_lock:
return await self._connection.fetch_one(self._build_query(query, values))

async def fetch_val(
self,
query: typing.Union[ClauseElement, str],
values: dict = None,
column: typing.Any = 0,
) -> typing.Any:
row = await self._connection.fetch_one(self._build_query(query, values))
async with self._query_lock:
row = await self._connection.fetch_one(self._build_query(query, values))
return None if row is None else row[column]

async def execute(
self, query: typing.Union[ClauseElement, str], values: dict = None
) -> typing.Any:
return await self._connection.execute(self._build_query(query, values))
async with self._query_lock:
return await self._connection.execute(self._build_query(query, values))

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]
await self._connection.execute_many(queries)
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]:
async for record in self._connection.iterate(self._build_query(query, values)):
yield record
async with self._query_lock:
async for record in self._connection.iterate(
self._build_query(query, values)
):
yield record

def transaction(self, *, force_rollback: bool = False) -> "Transaction":
return Transaction(self, force_rollback)
Expand Down
12 changes: 12 additions & 0 deletions tests/test_databases.py
Original file line number Diff line number Diff line change
Expand Up @@ -699,3 +699,15 @@ async def test_database_url_interface(database_url):
async with Database(database_url) as database:
assert isinstance(database.url, DatabaseURL)
assert database.url == database_url


@pytest.mark.parametrize("database_url", DATABASE_URLS)
@async_adapter
async def test_concurrent_access_on_single_connection(database_url):
async with Database(database_url, force_rollback=True) as database:

async def db_lookup():
if str(database_url).startswith("postgresql"):
await database.fetch_one("SELECT pg_sleep(1)")

await asyncio.gather(db_lookup(), db_lookup())