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3553522328
This pull request adds a new parameter to the REST Search API named `typed_keys`. When set to true, the aggregation names in the search response will be prefixed with a prefix that reflects the internal type of the aggregation.
Here is a simple example:
```
GET /_search?typed_keys
{
"aggs": {
"tweets_per_user": {
"terms": {
"field": "user"
}
}
},
"size": 0
}
```
And the response:
```
{
"aggs": {
"sterms:tweets_per_user": {
...
}
}
}
```
This parameter is intended to make life easier for REST clients that could parse back the prefix and could detect the type of the aggregation to parse. It could also be implemented for suggesters.
171 lines
5.3 KiB
Plaintext
171 lines
5.3 KiB
Plaintext
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[[caching-heavy-aggregations]]
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== Caching heavy aggregations
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Frequently used aggregations (e.g. for display on the home page of a website)
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can be cached for faster responses. These cached results are the same results
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that would be returned by an uncached aggregation -- you will never get stale
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results.
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See <<shard-request-cache>> for more details.
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[[returning-only-agg-results]]
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== Returning only aggregation results
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There are many occasions when aggregations are required but search hits are not. For these cases the hits can be ignored by
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setting `size=0`. For example:
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[source,js]
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--------------------------------------------------
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GET /twitter/tweet/_search
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{
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"size": 0,
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"aggregations": {
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"my_agg": {
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"terms": {
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"field": "text"
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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[setup:twitter]
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Setting `size` to `0` avoids executing the fetch phase of the search making the request more efficient.
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[[agg-metadata]]
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== Aggregation Metadata
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You can associate a piece of metadata with individual aggregations at request time that will be returned in place
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at response time.
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Consider this example where we want to associate the color blue with our `terms` aggregation.
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[source,js]
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--------------------------------------------------
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GET /twitter/tweet/_search
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{
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"size": 0,
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"aggs": {
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"titles": {
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"terms": {
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"field": "title"
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},
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"meta": {
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"color": "blue"
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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[setup:twitter]
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Then that piece of metadata will be returned in place for our `titles` terms aggregation
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[source,js]
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--------------------------------------------------
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{
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"aggregations": {
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"titles": {
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"meta": {
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"color" : "blue"
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},
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"doc_count_error_upper_bound" : 0,
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"sum_other_doc_count" : 0,
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"buckets": [
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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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// TESTRESPONSE[s/\.\.\./"took": "$body.took", "timed_out": false, "_shards": "$body._shards", "hits": "$body.hits"/]
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[[returning-aggregation-type]]
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== Returning the type of the aggregation
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Sometimes you need to know the exact type of an aggregation in order to parse its results. The `typed_keys` parameter
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can be used to change the aggregation's name in the response so that it will be prefixed by its internal type.
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Considering the following <<search-aggregations-bucket-datehistogram-aggregation,`date_histogram` aggregation>> named
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`tweets_over_time` which has a sub <<search-aggregations-metrics-top-hits-aggregation, 'top_hits` aggregation>> named
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`top_users`:
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[source,js]
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--------------------------------------------------
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GET /twitter/tweet/_search?typed_keys
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{
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"aggregations": {
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"tweets_over_time": {
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"date_histogram": {
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"field": "date",
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"interval": "year"
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},
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"aggregations": {
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"top_users": {
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"top_hits": {
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"size": 1
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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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--------------------------------------------------
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// CONSOLE
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// TEST[setup:twitter]
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In the response, the aggregations names will be changed to respectively `date_histogram:tweets_over_time` and
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`top_hits:top_users`, reflecting the internal types of each aggregation:
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[source,js]
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--------------------------------------------------
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{
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"aggregations": {
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"date_histogram#tweets_over_time": { <1>
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"buckets" : [
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{
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"key_as_string" : "2009-01-01T00:00:00.000Z",
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"key" : 1230768000000,
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"doc_count" : 5,
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"top_hits#top_users" : { <2>
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"hits" : {
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"total" : 5,
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"max_score" : 1.0,
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"hits" : [
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{
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"_index": "twitter",
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"_type": "tweet",
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"_id": "0",
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"_score": 1.0,
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"_source": {
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"date": "2009-11-15T14:12:12",
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"message": "trying out Elasticsearch",
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"user": "kimchy",
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"likes": 0
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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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]
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}
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},
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...
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}
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--------------------------------------------------
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// TESTRESPONSE[s/\.\.\./"took": "$body.took", "timed_out": false, "_shards": "$body._shards", "hits": "$body.hits"/]
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<1> The name `tweets_over_time` now contains the `date_histogram` prefix.
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<2> The name `top_users` now contains the `top_hits` prefix.
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NOTE: For some aggregations, it is possible that the returned type is not the same as the one provided with the
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request. This is the case for Terms, Significant Terms and Percentiles aggregations, where the returned type
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also contains information about the type of the targeted field: `lterms` (for a terms aggregation on a Long field),
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`sigsterms` (for a significant terms aggregation on a String field), `tdigest_percentiles` (for a percentile
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aggregation based on the TDigest algorithm).
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