mirror of https://github.com/apache/druid.git
84 lines
2.1 KiB
Markdown
84 lines
2.1 KiB
Markdown
---
|
||
layout: doc_page
|
||
---
|
||
Aggregations are specifications of processing over metrics available in Druid.
|
||
Available aggregations are:
|
||
|
||
### Count aggregator
|
||
|
||
`count` computes the row count that match the filters
|
||
|
||
```json
|
||
{ "type" : "count", "name" : <output_name> }
|
||
```
|
||
|
||
### Sum aggregators
|
||
|
||
#### `longSum` aggregator
|
||
|
||
computes the sum of values as a 64-bit, signed integer
|
||
|
||
```json
|
||
{ "type" : "longSum", "name" : <output_name>, "fieldName" : <metric_name> }
|
||
```
|
||
|
||
`name` – output name for the summed value
|
||
`fieldName` – name of the metric column to sum over
|
||
|
||
#### `doubleSum` aggregator
|
||
|
||
Computes the sum of values as 64-bit floating point value. Similar to `longSum`
|
||
|
||
```json
|
||
{ "type" : "doubleSum", "name" : <output_name>, "fieldName" : <metric_name> }
|
||
```
|
||
|
||
### Min / Max aggregators
|
||
|
||
#### `min` aggregator
|
||
|
||
`min` computes the minimum metric value
|
||
|
||
```json
|
||
{ "type" : "min", "name" : <output_name>, "fieldName" : <metric_name> }
|
||
```
|
||
|
||
#### `max` aggregator
|
||
|
||
`max` computes the maximum metric value
|
||
|
||
```json
|
||
{ "type" : "max", "name" : <output_name>, "fieldName" : <metric_name> }
|
||
```
|
||
|
||
### JavaScript aggregator
|
||
|
||
Computes an arbitrary JavaScript function over a set of columns (both metrics and dimensions).
|
||
|
||
All JavaScript functions must return numerical values.
|
||
|
||
```json
|
||
{ "type": "javascript", "name": "<output_name>",
|
||
"fieldNames" : [ <column1>, <column2>, ... ],
|
||
"fnAggregate" : "function(current, column1, column2, ...) {
|
||
<updates partial aggregate (current) based on the current row values>
|
||
return <updated partial aggregate>
|
||
}",
|
||
"fnCombine" : "function(partialA, partialB) { return <combined partial results>; }",
|
||
"fnReset" : "function() { return <initial value>; }"
|
||
}
|
||
```
|
||
|
||
**Example**
|
||
|
||
```json
|
||
{
|
||
"type": "javascript",
|
||
"name": "sum(log(x)/y) + 10",
|
||
"fieldNames": ["x", "y"],
|
||
"fnAggregate" : "function(current, a, b) { return current + (Math.log(a) * b); }",
|
||
"fnCombine" : "function(partialA, partialB) { return partialA + partialB; }",
|
||
"fnReset" : "function() { return 10; }"
|
||
}
|
||
```
|