druid/docs/content/TopNMetricSpec.md

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TopNMetricSpec
==================

The topN metric spec specifies how topN values should be sorted.

## Numeric TopNMetricSpec

The simplest metric specification is a String value indicating the metric to sort topN results by. They are included in a topN query with:

```json
"metric": <metric_value_string>
```

The metric field can also be given as a JSON object. The grammar for dimension values sorted by numeric value is shown below:

```json
"metric": {
    "type": "numeric",
    "metric": "<metric_value>"
}
```

|property|description|required?|
|--------|-----------|---------|
|type|this indicates a numeric sort|yes|
|metric|the actual metric field in which results will be sorted by|yes|

## Lexicographic TopNMetricSpec

The grammar for dimension values sorted lexicographically is as follows:

```json
"metric": {
    "type": "lexicographic",
    "previousStop": "<previousStop_value>"
}
```

|property|description|required?|
|--------|-----------|---------|
|type|this indicates a lexicographic sort|yes|
|previousStop|the starting point of the lexicographic sort. For example, if a previousStop value is 'b', all values before 'b' are discarded. This field can be used to paginate through all the dimension values.|no|

## AlphaNumeric TopNMetricSpec

Sort dimension values in alpha-numeric order, i.e treating numbers differently from other characters in sorting the values.
See [http://www.davekoelle.com/alphanum.html](http://www.davekoelle.com/alphanum.html) for details on how the algorithm works.

```json
"metric": {
    "type": "alphaNumeric",
    "previousStop": "<previousStop_value>"
}
```

|property|description|required?|
|--------|-----------|---------|
|type|this indicates an alpha-numeric sort|yes|
|previousStop|the starting point of the alpha-numeric sort. For example, if a previousStop value is 'b', all values before 'b' are discarded. This field can be used to paginate through all the dimension values.|no|

## Inverted TopNMetricSpec

Sort dimension values in inverted order, i.e inverts the order of the delegate metric spec. It can be used to sort the values in descending order.

```json
"metric": {
    "type": "inverted",
    "metric": <delegate_top_n_metric_spec>
}
```

|property|description|required?|
|--------|-----------|---------|
|type|this indicates an inverted sort|yes|
|metric|the delegate metric spec. |yes|