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9b3c85dd88
_field_stats has evolved quite a lot to become a multi purpose API capable of retrieving the field capabilities and the min/max value for a field. In the mean time a more focused API called `_field_caps` has been added, this enpoint is a good replacement for _field_stats since he can retrieve the field capabilities by just looking at the field mapping (no lookup in the index structures). Also the recent improvement made to range queries makes the _field_stats API obsolete since this queries are now rewritten per shard based on the min/max found for the field. This means that a range query that does not match any document in a shard can return quickly and can be cached efficiently. For these reasons this change deprecates _field_stats. The deprecation should happen in 5.4 but we won't remove this API in 6.x yet which is why this PR is made directly to 6.0. The rest tests have also been adapted to not throw an error while this change is backported to 5.4.
382 lines
12 KiB
Plaintext
382 lines
12 KiB
Plaintext
[[search-field-stats]]
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== Field stats API
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experimental[]
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deprecated[5.4.0, `_field_stats` is deprecated, use `_field_caps` instead or run an min/max aggregation on the desired fields]
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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
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specific indices too.
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All indices:
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[source,js]
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--------------------------------------------------
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GET _field_stats?fields=rating
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--------------------------------------------------
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// CONSOLE
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// TEST[warning:[_field_stats] endpoint is deprecated! Use [_field_caps] instead or run a min/max aggregations on the desired fields.]
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Specific indices:
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[source,js]
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--------------------------------------------------
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GET twitter/_field_stats?fields=rating
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--------------------------------------------------
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// CONSOLE
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// TEST[warning:[_field_stats] endpoint is deprecated! Use [_field_caps] instead or run a min/max aggregations on the desired fields.]
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// TEST[setup:twitter]
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Supported request options:
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[horizontal]
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`fields`:: A list of fields to compute stats for. The field name supports wildcard notation. For example, using `text_*`
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will cause all fields that match the expression to be returned.
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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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Alternatively the `fields` option can also be defined in the request body:
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[source,js]
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--------------------------------------------------
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POST _field_stats?level=indices
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{
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"fields" : ["rating"]
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}
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--------------------------------------------------
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// CONSOLE
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// TEST[warning:[_field_stats] endpoint is deprecated! Use [_field_caps] instead or run a min/max aggregations on the desired fields.]
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This is equivalent to the previous request.
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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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[horizontal]
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`max_doc`::
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The total number of documents.
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`doc_count`::
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The number of documents that have at least one term for this field, or -1 if
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this measurement isn't available on one or more shards.
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`density`::
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The percentage of documents that have at least one value for this field. This
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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.
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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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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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`is_searchable`
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True if any of the instances of the field is searchable, false otherwise.
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`is_aggregatable`
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True if any of the instances of the field is aggregatable, false otherwise.
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`min_value`::
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The lowest value in the field.
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`min_value_as_string`::
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The lowest value in the field represented in a displayable form. All fields,
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but string fields returns this. (since string fields, represent values already as strings)
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`max_value`::
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The highest value in the field.
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`max_value_as_string`::
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The highest value in the field represented in a displayable form. All fields,
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but string fields returns this. (since string fields, represent values already as strings)
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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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=== Cluster level field statistics example
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Request:
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[source,js]
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--------------------------------------------------
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GET _field_stats?fields=rating,answer_count,creation_date,display_name
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--------------------------------------------------
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// CONSOLE
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// TEST[warning:[_field_stats] endpoint is deprecated! Use [_field_caps] instead or run a min/max aggregations on the desired fields.]
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Response:
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[source,js]
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--------------------------------------------------
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{
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"_shards": {
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"total": 1,
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"successful": 1,
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"failed": 0
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},
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"indices": {
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"_all": { <1>
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"fields": {
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"creation_date": {
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"max_doc": 1326564,
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"doc_count": 564633,
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"density": 42,
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"sum_doc_freq": 2258532,
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"sum_total_term_freq": -1,
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"min_value": "2008-08-01T16:37:51.513Z",
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"max_value": "2013-06-02T03:23:11.593Z",
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"is_searchable": "true",
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"is_aggregatable": "true"
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},
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"display_name": {
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"max_doc": 1326564,
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"doc_count": 126741,
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"density": 9,
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"sum_doc_freq": 166535,
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"sum_total_term_freq": 166616,
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"min_value": "0",
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"max_value": "정혜선",
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"is_searchable": "true",
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"is_aggregatable": "false"
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},
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"answer_count": {
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"max_doc": 1326564,
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"doc_count": 139885,
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"density": 10,
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"sum_doc_freq": 559540,
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"sum_total_term_freq": -1,
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"min_value": 0,
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"max_value": 160,
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"is_searchable": "true",
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"is_aggregatable": "true"
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},
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"rating": {
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"max_doc": 1326564,
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"doc_count": 437892,
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"density": 33,
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"sum_doc_freq": 1751568,
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"sum_total_term_freq": -1,
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"min_value": -14,
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"max_value": 1277,
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"is_searchable": "true",
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"is_aggregatable": "true"
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}
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}
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}
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}
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}
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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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NOTE: When using the cluster level field statistics it is possible to have conflicts if the same field is used in
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different indices with incompatible types. For instance a field of type `long` is not compatible with a field of
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type `float` or `string`. A section named `conflicts` is added to the response if one or more conflicts are raised.
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It contains all the fields with conflicts and the reason of the incompatibility.
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[source,js]
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--------------------------------------------------
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{
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"_shards": {
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"total": 1,
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"successful": 1,
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"failed": 0
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},
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"indices": {
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"_all": {
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"fields": {
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"creation_date": {
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"max_doc": 1326564,
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"doc_count": 564633,
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"density": 42,
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"sum_doc_freq": 2258532,
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"sum_total_term_freq": -1,
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"min_value": "2008-08-01T16:37:51.513Z",
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"max_value": "2013-06-02T03:23:11.593Z",
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"is_searchable": "true",
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"is_aggregatable": "true"
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}
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}
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}
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},
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"conflicts": {
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"field_name_in_conflict1": "reason1",
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"field_name_in_conflict2": "reason2"
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}
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}
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--------------------------------------------------
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[float]
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==== Indices level field statistics example
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Request:
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[source,js]
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--------------------------------------------------
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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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// CONSOLE
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// TEST[warning:[_field_stats] endpoint is deprecated! Use [_field_caps] instead or run a min/max aggregations on the desired fields.]
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Response:
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[source,js]
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--------------------------------------------------
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{
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"_shards": {
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"total": 1,
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"successful": 1,
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"failed": 0
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},
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"indices": {
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"stack": { <1>
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"fields": {
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"creation_date": {
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"max_doc": 1326564,
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"doc_count": 564633,
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"density": 42,
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"sum_doc_freq": 2258532,
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"sum_total_term_freq": -1,
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"min_value": "2008-08-01T16:37:51.513Z",
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"max_value": "2013-06-02T03:23:11.593Z",
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"is_searchable": "true",
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"is_aggregatable": "true"
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},
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"display_name": {
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"max_doc": 1326564,
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"doc_count": 126741,
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"density": 9,
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"sum_doc_freq": 166535,
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"sum_total_term_freq": 166616,
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"min_value": "0",
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"max_value": "정혜선",
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"is_searchable": "true",
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"is_aggregatable": "false"
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},
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"answer_count": {
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"max_doc": 1326564,
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"doc_count": 139885,
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"density": 10,
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"sum_doc_freq": 559540,
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"sum_total_term_freq": -1,
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"min_value": 0,
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"max_value": 160,
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"is_searchable": "true",
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"is_aggregatable": "true"
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},
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"rating": {
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"max_doc": 1326564,
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"doc_count": 437892,
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"density": 33,
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"sum_doc_freq": 1751568,
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"sum_total_term_freq": -1,
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"min_value": -14,
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"max_value": 1277,
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"is_searchable": "true",
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"is_aggregatable": "true"
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}
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}
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}
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}
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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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[float]
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=== Field stats index constraints
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Field stats index constraints allows to omit all field stats for indices that don't match with the constraint. An index
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constraint can exclude indices' field stats based on the `min_value` and `max_value` statistic. This option is only
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useful if the `level` option is set to `indices`. Fields that are not indexed (not searchable) are always omitted when an index constraint is defined.
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For example index constraints can be useful to find out the min and max value of a particular property of your data in
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a time based scenario. The following request only returns field stats for the `answer_count` property for indices
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holding questions created in the year 2014:
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[source,js]
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--------------------------------------------------
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POST _field_stats?level=indices
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{
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"fields" : ["answer_count"], <1>
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"index_constraints" : { <2>
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"creation_date" : { <3>
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"max_value" : { <4>
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"gte" : "2014-01-01T00:00:00.000Z"
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},
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"min_value" : { <4>
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"lt" : "2015-01-01T00:00:00.000Z"
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}
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}
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}
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}
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--------------------------------------------------
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// CONSOLE
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// TEST[warning:[_field_stats] endpoint is deprecated! Use [_field_caps] instead or run a min/max aggregations on the desired fields.]
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<1> The fields to compute and return field stats for.
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<2> The set index constraints. Note that index constrains can be defined for fields that aren't defined in the `fields` option.
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<3> Index constraints for the field `creation_date`.
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<4> Index constraints on the `max_value` and `min_value` property of a field statistic.
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For a field, index constraints can be defined on the `min_value` statistic, `max_value` statistic or both.
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Each index constraint support the following comparisons:
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[horizontal]
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`gte`:: Greater-than or equal to
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`gt`:: Greater-than
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`lte`:: Less-than or equal to
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`lt`:: Less-than
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Field stats index constraints on date fields optionally accept a `format` option, used to parse the constraint's value.
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If missing, the format configured in the field's mapping is used.
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[source,js]
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--------------------------------------------------
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POST _field_stats?level=indices
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{
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"fields" : ["answer_count"],
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"index_constraints" : {
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"creation_date" : {
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"max_value" : {
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"gte" : "2014-01-01",
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"format" : "date_optional_time" <1>
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},
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"min_value" : {
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"lt" : "2015-01-01",
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"format" : "date_optional_time"
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}
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}
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}
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}
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--------------------------------------------------
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// CONSOLE
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// TEST[warning:[_field_stats] endpoint is deprecated! Use [_field_caps] instead or run a min/max aggregations on the desired fields.]
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<1> Custom date format
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