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Field Stats Plugin for Elasticsearch

This plugin provides a feature very similar to Field Stats native Elasticsearch functionality that has been removed from Elasticsearch starting from version 6.0. It imitates the old functionality and is compatible with the old API.

Read more about potential use cases in the blog post Field Stats for Elasticsearch 6.x.

Installation

Make sure to change the version number in the download URL based on your ES version. You can find available releases here: https://github.com/sematext/elasticsearch-field-stats/releases. The plugin version must match your Elasticsearch version. Feel free to contribute new version if your version is not supported Elasticsearch version which you use.

bin/elasticsearch-plugin install URL

Example for ES 6.4.1:

bin/plugin install https://github.com/sematext/elasticsearch-field-stats/releases/download/v6.4.1/field-stats-6.4.1.zip

Usage

The field stats API lets one find statistical properties of a field without executing an expensive aggregation by looking up measurements that are natively available in the Lucene index. This can be useful to explore a dataset that you don’t know much about. For example, this allows finding indices that should be queried based on min/max date they store with meaningful.

GET logs*/_field_stats?fields=timestamp

Supported request options:

Parameter Description
fields A list of fields to compute stats for. The field name supports wildcard notation. For example, using text_* will cause all fields that match the expression to be returned.
level Defines if field stats should be returned on a per index level or on a cluster wide level. Valid values are indices and cluster (default).

Alternatively, the fields option can also be defined in the request body:

POST _field_stats?level=indices
{
   "fields" : ["timestamp"]
}

Field statistics

The field stats API is supported on string-based, number-based and date-based fields and can return the following statistics per field:

Parameter Description
max_doc The total number of documents.
doc_count The number of documents that have at least one term for this field, or -1 if this measurement isn’t available on one or more shards.
density The percentage of documents that have at least one value for this field. This is a derived statistic and is based on the max_doc and doc_count.
sum_doc_freq The sum of each term’s document frequency in this field, or -1 if this measurement isn’t available on one or more shards. Document frequency is the number of documents containing a particular term.
sum_total_term_freq The sum of the term frequencies of all terms in this field across all documents, or -1 if this measurement isn’t available on one or more shards. Term frequency is the total number of occurrences of a term in a particular document and field.
min_value The lowest value in the field.
min_value_as_string The lowest value in the field represented in a displayable form. All fields, but string fields returns this. (since string fields, represent values already as strings)
max_value The highest value in the field.
max_value_as_string The highest value in the field represented in a displayable form. All fields, but string fields returns this. (since string fields, represent values already as strings)

Note

It is very important to note that documents marked as deleted (but not yet removed by internal Lucene merge process) still affect all the mentioned statistics. Keep this in mind and use field stats wisely. This is very useful especially for environemnts with append-only indices.

Build and contribution

In order to install this plugin, you need to create a zip distribution.

./gradlew build

This will produce a zip file in build/distributions. After building the zip file, you can install it like this

bin/plugin install file:///path/to/elasticsearch-field-stats/build/distribution/elasticsearch-field-stats-<VERSION>.zip

Feel free to prepare pull requests.

Licenses

This repository in distributed under Apache License. Feel free to use and contribute!