Docs: Tidied up the field statistics docs
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Clinton Gormley
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@ -3,11 +3,14 @@
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experimental[]
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The field stats api allows one to find statistical properties of a field without executing a search, but
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looking up measurements that are natively available in the Lucene index. This can be useful to explore a dataset which
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you don't know much about. For example, this allows creating a histogram aggregation with meaningful intervals.
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The field stats api allows one to find statistical properties of a field
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without executing a search, but looking up measurements that are natively
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available in the Lucene index. This can be useful to explore a dataset which
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you don't know much about. For example, this allows creating a histogram
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aggregation with meaningful intervals based on the min/max range of values.
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The field stats api by defaults executes on all indices, but can execute on specific indices too.
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The field stats api by defaults executes on all indices, but can execute on
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specific indices too.
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All indices:
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@ -26,15 +29,11 @@ curl -XGET "http://localhost:9200/index1,index2/_field_stats?fields=rating"
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Supported request options:
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[horizontal]
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`fields`::
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A list of fields to compute stats for.
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`level`::
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Defines if field stats should be returned on a per index level or on a cluster
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wide level. Valid values are `indices` and `cluster`. Defaults to `cluster`.
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`fields`:: A list of fields to compute stats for.
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`level`:: Defines if field stats should be returned on a per index level or on a
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cluster wide level. Valid values are `indices` and `cluster` (default).
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[float]
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=== Field statistics
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The field stats api is supported on string based, number based and date based fields and can return the following statistics per field:
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@ -57,13 +56,13 @@ is a derived statistic and is based on the `max_doc` and `doc_count`.
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`sum_doc_freq`::
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The sum of each term's document frequency in this field, or -1 if this
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measurement isn't available on one or more shards. Document frequency is the
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number of documents containing a particular term.
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measurement isn't available on one or more shards.
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Document frequency is the number of documents containing a particular term.
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`sum_total_term_freq`::
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The sum of the term frequencies of all terms in this field across all
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documents, or `-1` if this measurement isn't available on one or more shards.
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documents, or -1 if this measurement isn't available on one or more shards.
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Term frequency is the total number of occurrences of a term in a particular
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document and field.
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@ -75,18 +74,19 @@ The lowest value in the field represented in a displayable form.
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The highest value in the field represented in a displayable form.
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NOTE: For all the mentioned statistics, documents marked as deleted aren't taken into account. The documents marked
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as deleted are are only taken into account when the segments these documents reside on are merged away.
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NOTE: Documents marked as deleted (but not yet removed by the merge process)
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still affect all the mentioned statistics.
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[float]
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=== Example
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.Cluster level field statistics
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==================================================
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[source,js]
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--------------------------------------------------
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curl -XGET "http://localhost:9200/_field_stats?fields=rating,answer_count,creation_date,display_name"
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GET /_field_stats?fields=rating,answer_count,creation_date,display_name
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--------------------------------------------------
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[source,js]
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[source,json]
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--------------------------------------------------
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{
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"_shards": {
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@ -140,12 +140,14 @@ curl -XGET "http://localhost:9200/_field_stats?fields=rating,answer_count,creati
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--------------------------------------------------
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<1> The `_all` key indicates that it contains the field stats of all indices in the cluster.
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==================================================
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With level set to `indices`:
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.Indices level field statistics
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==================================================
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[source,js]
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--------------------------------------------------
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curl -XGET "http://localhost:9200/_field_stats?fields=rating,answer_count,creation_date,display_name&level=indices"
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GET /_field_stats?fields=rating,answer_count,creation_date,display_name&level=indices
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--------------------------------------------------
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[source,js]
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@ -201,4 +203,6 @@ curl -XGET "http://localhost:9200/_field_stats?fields=rating,answer_count,creati
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}
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--------------------------------------------------
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<1> The `stack` key means it contains all field stats for the `stack` index.
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<1> The `stack` key means it contains all field stats for the `stack` index.
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==================================================
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