NDB 查询 fetch() 和 ContextOptions [英] NDB query fetch() and ContextOptions

问题描述

我只想在我的一个查询中禁用上下文缓存.我以为我可以这样做:

I would like to disable context cache in only one of my queries. I thought I could do it like this:

MyModel.query(ancestor=user.key).fetch(100, options=ContextOptions(use_cache=False, use_memcache=False))

或

MyModel.query(ancestor=user.key).fetch(100, config=ContextOptions(use_cache=False, use_memcache=False))

但它似乎对我不起作用.所以我的问题是如何使用 fetch 为查询禁用缓存和内存缓存?

But it does not seem to work for me. So my question is how do I disable cache and memcache for queries using fetch?

附注:

对于 get() 它完美地工作:

For get() it works perfectly:

MyModel.query(ancestor=user.key).get(use_cache=False, use_memcache=False)

谢谢！

推荐答案

缓存仅支持 get() 的.来自文档:

Caching is supported only for get()'s. From the docs:

查询不会在任何缓存中查找值.但是，查询结果是如果缓存策略如此写回上下文缓存(但永远不要去Memcache).

Queries do not look up values in any cache. However, query results are written back to the in-context cache if the cache policy says so (but never to Memcache).

如果您遇到某些实体的问题，这些实体似乎已被缓存，您可能需要更改上下文缓存策略:

If you are experiencing problems with some entities, which seem to be cached, you probably have to change context cache policy:

ctx.set_cache_policy(lambda key: False)

set_cache_policy 的参数必须是一个函数，如果必须缓存键，则返回一个参数(键)并返回布尔值.这里它总是返回 False，所以不会缓存任何实体.

Argument of set_cache_policy has to be function taking one param (key) and returning boolean if the key has to be cached. Here it always returns False, so no entity will be cached.

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