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- $limit (aggregation)
$limit (aggregation)¶
-
$limit
¶ Restricts the number of documents that pass through the
$limit
in the pipeline.$limit
takes a single numeric (positive whole number) value as a parameter. Once the specified number of documents pass through the pipeline operator, no more will. Consider the following example:This operation returns only the first 5 documents passed to it from by the pipeline.
$limit
has no effect on the content of the documents it passes.Note
Changed in version 2.4:
$sort
and memory requirements:- When a
$sort
immediately precedes a$limit
in the pipeline, the$sort
operation only maintains the top n results as it progresses, where n is the specified limit, and MongoDB only needs to store the number of items specified by$limit
in memory. Before MongoDB 2.4,$sort
would sort all the results in memory, and then limit the results to n results. - Unless the
$sort
operator can use an index or immediately precedes a$limit
, the$sort
operation must fit within memory. Before MongoDB 2.4, unless the$sort
operator can use an index, the$sort
operation must fit within memory.
$sort
produces an error if the operation consumes 10 percent or more of RAM.- When a