[GitHub] jon-wei commented on a change in pull request #6638: Fixed buckets histogram aggregator

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jon-wei commented on a change in pull request #6638: Fixed buckets histogram aggregator
URL: https://github.com/apache/incubator-druid/pull/6638#discussion_r244888775
 
 

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 File path: docs/content/development/extensions-core/approximate-histograms.md
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 @@ -91,17 +95,138 @@ query.
 |`numBuckets`             |Number of output buckets for the resulting histogram. Bucket intervals are dynamic, based on the range of the underlying data. Use a post-aggregator to have finer control over the bucketing scheme|7|
 |`lowerLimit`/`upperLimit`|Restrict the approximation to the given range. The values outside this range will be aggregated into two centroids. Counts of values outside this range are still maintained. |-INF/+INF|
 
+## Fixed Buckets Histogram
+
+The fixed buckets histogram aggregator builds a histogram on a numeric column, with evenly-sized buckets across a specified value range. Values outside of the range are handled based on a user-specified outlier handling mode.
+
+This histogram supports the min/max/quantiles post-aggregators but does not support the bucketing post-aggregators.
+
+
+|Property                 |Description                   |Default                           |
+|-------------------------|------------------------------|----------------------------------|
+|`type`|Type of the aggregator. Must `fixedBucketsHistogram`.|No default, must be specified|
+|`name`|Column name for the aggregator.|No default, must be specified|
+|`fieldName`|Column name of the input to the aggregator.|No default, must be specified|
+|`lowerLimit`|Lower limit of the histogram. |No default, must be specified|
+|`upperLimit`|Upper limit of the histogram. |No default, must be specified|
+|`numBuckets`|Number of buckets for the histogram. The range [lowerLimit, upperLimit] will be divided into `numBuckets` intervals of equal size.|10|
+|`outlierHandlingMode`|Specifies how values outside of [lowerLimit, upperLimit] will be handled. Supported modes are "ignore", "overflow", and "clip". See [outlier handling modes](#outlier-handling-modes) for more details.|No default, must be specified|
+
+An example aggregator spec is shown below:
+
+```json
+{
+  "type" : "fixedBucketsHistogram",
+  "name" : <output_name>,
+  "fieldName" : <metric_name>,
+  "numBuckets" : <integer>,
+  "lowerLimit" : <double>,
+  "upperLimit" : <double>,
+  "outlierHandlingMode": <mode>
+}
+```
+
+### Outlier handling modes
+
+The outlier handling mode specifies what should be done with values outside of the histogram's range. There are three supported modes:
 
 Review comment:
   Added some details on that

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