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add docs

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Xavier Léauté 2014-10-21 17:24:44 -07:00
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docs/content/Aggregations.md
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@ -160,3 +160,28 @@ Uses [HyperLogLog](http://algo.inria.fr/flajolet/Publications/FlFuGaMe07.pdf) to
```json
{ "type" : "hyperUnique", "name" : <output_name>, "fieldName" : <metric_name> }
```
## Miscellaneous Aggregations
### Filtered Aggregator
A filtered aggregator wraps any given aggregator, but only aggregates the values for which the given dimension filter matches.
This makes it possible to compute the results of a filtered and an unfiltered aggregation simultaneously, without having to issue multiple queries, and use both results as part of post-aggregations.
*Limitations:* The filtered aggregator currently only supports selector filters, i.e. matching a dimension against a single value.
*Note:* If only the filtered results are required, consider putting the filter on the query itself, which will be much faster since it does not require scanning all the data.
```json
{
"type" : "filtered",
"name" : "aggMatching",
"filter" : {
"type" : "selector",
"dimension" : <dimension>,
"value" : <dimension value>
}
"aggregator" : <aggregation>
}
```