MongoDB 索引中的空值如何排序? [英] How are null values in a MongoDB index sorted?

问题描述

我想以特定方式 (-1, 1) 对索引进行排序，并希望确保空值位于索引的顶部.我如何确保这一点?

I want to sort my index in a specific way (-1, 1) and want to make sure that null values are at the top of the index. How can I ensure this?

推荐答案

如果您按降序排序并且在末尾看到 null 值，这将是排序的默认行为.

If you are sorting descending and you are seeing null values at the end, that would be the default behaviour of the sort.

实际上没有太多可以改变这种行为的方法，但是可以为您提供所需结果的解决方法是执行两个查询而不是一个:

There's really not much that can be done to change that behaviour, but a workaround that will give you the results you're looking for is to do two queries instead of one:

db.Collection.find( { a: null } );
db.Collection.find( { a: { $ne: null } } ).sort( { a: -1, b: 1 } );

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