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- Aggregation Pipeline Operators >
- Pipeline Aggregation Stages >
- $limit (aggregation)
$limit (aggregation)¶
Definition¶
Example¶
Consider the following example:
db.article.aggregate(
{ $limit : 5 }
);
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.
注解
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 n items in memory. This optimization still applies when allowDiskUse is true and the n items exceed the aggregation memory limit.
在 2.4 版更改: Before MongoDB 2.4, $sort would sort all the results in memory, and then limit the results to n results.