170 lines
6.2 KiB
Plaintext
170 lines
6.2 KiB
Plaintext
[[search-field-stats]]
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== Field stats API
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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 by defaults executes on all indices, but can execute on specific indices too.
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All indices:
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[source,js]
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--------------------------------------------------
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curl -XGET "http://localhost:9200/_field_stats?fields=rating"
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--------------------------------------------------
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Specific indices:
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[source,js]
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--------------------------------------------------
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curl -XGET "http://localhost:9200/index1,index2/_field_stats?fields=rating"
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--------------------------------------------------
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Supported request options:
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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 cluster wide level. Valid values are
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`indices` and `cluster`. Defaults to `cluster`.
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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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* `max_doc` - The total number of documents.
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* `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.
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* `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`.
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* `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.
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Document frequency is the number of documents containing a particular term.
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* `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.
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Term frequency is the total number of occurrences of a term in a particular document and field.
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* `min_value` - The lowest value in the field represented in a displayable form.
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* `max_value` - The highest value in the field represented in a displayable form.
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Note that 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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=== Example
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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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--------------------------------------------------
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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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},
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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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},
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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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},
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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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}
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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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With level set to `indices`:
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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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--------------------------------------------------
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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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},
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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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},
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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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},
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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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}
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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. |