Aggregation Framework - $sort

Overview
Specification
Notes

Overview

The $sort pipeline operator sorts its input documents.

Specification

db.<collection-name>.aggregate(
    { $sort : { <sort-key> } }
);

$sort requires a sort key. Sort key specifications are exactly the same as those for
indexing (see Indexes - Basics and Indexes - Compound Keys Indexes). A sort key is a series of field-value pairs, each of which specifies a 1 or -1 for its value to indicate an ascending or descending sort, as shown by this example:

db.sortex.aggregate(
    { $sort : { b : -1, a: 1 } }
);

Here, the output will be the sorted collection, sorted by "b" descending, and "a" ascending.

Notes

The $sort operator cannot produce any output documents until it has seen all of its input. It will exhaust the prior pipeline operator's output, sort what it has received, and then be ready to produce output.

At the present time, sorts must fit in memory, so sorting a large input stream may not work.

Aggregation Framework - $sort

Overview

Specification

Notes

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