Django
官网有形容
Django 异步的变动
- 4.2 相比于 4.0 的变动就是应用 sync_to_async
- 最大的变动就是能够应用同步和异步互不影响
异步实现
models 文件夹下的 query 文件
class BaseIterable:
def __init__(self, queryset, chunked_fetch=False, chunk_size=GET_ITERATOR_CHUNK_SIZE):
self.queryset = queryset
self.chunked_fetch = chunked_fetch
self.chunk_size = chunk_size
async def _async_generator(self):
# Generators don't actually start running until the first time you call
# next() on them, so make the generator object in the async thread and
# then repeatedly dispatch to it in a sync thread.
sync_generator = self.__iter__()
def next_slice(gen):
return list(islice(gen, self.chunk_size))
while True:
chunk = await sync_to_async(next_slice)(sync_generator)
for item in chunk:
yield item
if len(chunk) < self.chunk_size:
break
# __aiter__() is a *synchronous* method that has to then return an
# *asynchronous* iterator/generator. Thus, nest an async generator inside
# it.
# This is a generic iterable converter for now, and is going to suffer a
# performance penalty on large sets of items due to the cost of crossing
# over the sync barrier for each chunk. Custom __aiter__() methods should
# be added to each Iterable subclass, but that needs some work in the
# Compiler first.
def __aiter__(self):
return self._async_generator()
class ModelIterable(BaseIterable):
"""Iterable that yields a model instance for each row."""
def __iter__(self):
代码省略
class QuerySet(AltersData):
"""Represent a lazy database lookup for a set of objects."""
def __init__(self, model=None, query=None, using=None, hints=None):
self._iterable_class = ModelIterable
def __aiter__(self):
# Remember, __aiter__ itself is synchronous, it's the thing it returns
# that is async!
async def generator():
await sync_to_async(self._fetch_all)()
for item in self._result_cache:
yield item
return generator()论断
- 就是__aiter__ 实现了 async for 办法，具体的 await obj 是通过 sync_to_async 实现
- 感觉 ORM 层面的异步和同步区别不大，毕竟在数据连贯层面没有变动
- 临时看进去的就这么多，技术无限，后续持续跟进