Morphia/MongoDB：如何迭代不同的字段

发布于 2024-10-17 12:08:01 字数 307 浏览 2 评论 0原文

我想迭代给定文档中不同字段的列表。使用 MongoDB 命令行，我可以通过执行以下操作来获得我想要的东西：

db.MyDoc.distinct("someField")

...只不过它以巨大的 BSON 形式返回所有结果。

有没有办法在 Morphia 中做到这一点，并进一步将其作为 Iterable 返回，以便所有结果不会一次读入内存？

我认为 distinct() 是作为某种内存中哈希图实现的，这可能意味着我尝试逐步迭代结果以避免将它们全部放入内存中是没有意义的。

原文

I'd like to iterate over a list of distinct fields in a given document. Using the MongoDB command line, I can kind of get what I want by doing something like:

db.MyDoc.distinct("someField")

... except that it returns all the results as a giant BSON.

Is there a way to do this in Morphia, and to furthermore return it as an Iterable, so that all the results are not read into memory all at once?

I imagine that distinct() is implemented as some kind of in-memory hashmap, which probably means that there's no point in my trying to iterate over the results piecemeal to avoid having them all in memory at once.

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