mongodb - What is the difference between $push/$sort and .sort() at query time? -


so, retrieval purposes, difference between two? think $push/$sort feature new in 2.4 yet still don't understand how different using .sort() on sub-document array while querying parent. using $push/$sort better approach? save use of index on subdoc array?

2.4 introduced feature allows keep "last/best/top/first" n elements of array when $push new values during update. way specifying field , direction use $sort , $slice tell how many keep.

when query , use sort() applies documents being returned, not elements of arrays inside of such documents.

see more description of capped array feature here.


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