Histogram field type

histogram fields are primarily intended for use with aggregations. To make it more readily accessible for aggregations, histogram field data is stored as a binary doc values and not indexed. Its size in bytes is at most 13 * numValues, where numValues is the length of the provided arrays.

Because the data is not indexed, you only can use histogram fields for the following aggregations and queries:

When using a histogram as part of an aggregation, the accuracy of the results will depend on how the histogram was constructed. It is important to consider the percentiles aggregation mode that will be used to build it. Some possibilities include:

The histogram field is "algorithm agnostic" and does not store data specific to either T-Digest or HDRHistogram. While this means the field can technically be aggregated with either algorithm, in practice the user should chose one algorithm and index data in that manner (e.g. centroids for T-Digest or intervals for HDRHistogram) to ensure best accuracy.

The following create index API request creates a new index with two field mappings:

PUT my-index-000001
{
  "mappings" : {
    "properties" : {
      "my_histogram" : {
        "type" : "histogram"
      },
      "my_text" : {
        "type" : "keyword"
      }
    }
  }
}

The following index API requests store pre-aggregated for two histograms: histogram_1 and histogram_2.

PUT my-index-000001/_doc/1
{
  "my_text" : "histogram_1",
  "my_histogram" : {
      "values" : [0.1, 0.2, 0.3, 0.4, 0.5], 
      "counts" : [3, 7, 23, 12, 6] 
   }
}

PUT my-index-000001/_doc/2
{
  "my_text" : "histogram_2",
  "my_histogram" : {
      "values" : [0.1, 0.25, 0.35, 0.4, 0.45, 0.5], 
      "counts" : [8, 17, 8, 7, 6, 2] 
   }
}