590 lines
19 KiB
Plaintext
590 lines
19 KiB
Plaintext
[[search-aggregations-bucket-composite-aggregation]]
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=== Composite Aggregation
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A multi-bucket aggregation that creates composite buckets from different sources.
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Unlike the other `multi-bucket` aggregation the `composite` aggregation can be used
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to paginate **all** buckets from a multi-level aggregation efficiently. This aggregation
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provides a way to stream **all** buckets of a specific aggregation similarly to what
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<<request-body-search-scroll, scroll>> does for documents.
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The composite buckets are built from the combinations of the
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values extracted/created for each document and each combination is considered as
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a composite bucket.
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//////////////////////////
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[source,js]
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--------------------------------------------------
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PUT /sales
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{
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"mappings": {
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"properties": {
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"product": {
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"type": "keyword"
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},
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"timestamp": {
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"type": "date"
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},
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"price": {
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"type": "long"
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},
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"shop": {
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"type": "keyword"
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},
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"nested": {
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"type": "nested",
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"properties": {
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"product": {
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"type": "keyword"
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},
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"timestamp": {
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"type": "date"
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},
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"price": {
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"type": "long"
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},
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"shop": {
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"type": "keyword"
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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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POST /sales/_bulk?refresh
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{"index":{"_id":0}}
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{"product": "mad max", "price": "20", "timestamp": "2017-05-09T14:35"}
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{"index":{"_id":1}}
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{"product": "mad max", "price": "25", "timestamp": "2017-05-09T12:35"}
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{"index":{"_id":2}}
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{"product": "rocky", "price": "10", "timestamp": "2017-05-08T09:10"}
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{"index":{"_id":3}}
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{"product": "mad max", "price": "27", "timestamp": "2017-05-10T07:07"}
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{"index":{"_id":4}}
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{"product": "apocalypse now", "price": "10", "timestamp": "2017-05-11T08:35"}
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-------------------------------------------------
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// NOTCONSOLE
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// TESTSETUP
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//////////////////////////
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For instance the following document:
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[source,js]
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--------------------------------------------------
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{
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"keyword": ["foo", "bar"],
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"number": [23, 65, 76]
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}
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--------------------------------------------------
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// NOTCONSOLE
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\... creates the following composite buckets when `keyword` and `number` are used as values source
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for the aggregation:
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[source,js]
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--------------------------------------------------
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{ "keyword": "foo", "number": 23 }
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{ "keyword": "foo", "number": 65 }
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{ "keyword": "foo", "number": 76 }
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{ "keyword": "bar", "number": 23 }
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{ "keyword": "bar", "number": 65 }
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{ "keyword": "bar", "number": 76 }
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--------------------------------------------------
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// NOTCONSOLE
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==== Values source
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The `sources` parameter controls the sources that should be used to build the composite buckets.
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The order that the `sources` are defined is important because it also controls the order
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the keys are returned.
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The name given to each sources must be unique.
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There are three different types of values source:
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===== Terms
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The `terms` value source is equivalent to a simple `terms` aggregation.
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The values are extracted from a field or a script exactly like the `terms` aggregation.
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Example:
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[source,console]
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--------------------------------------------------
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GET /_search
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{
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"aggs" : {
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"my_buckets": {
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"composite" : {
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"sources" : [
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{ "product": { "terms" : { "field": "product" } } }
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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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Like the `terms` aggregation it is also possible to use a script to create the values for the composite buckets:
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[source,console]
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--------------------------------------------------
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GET /_search
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{
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"aggs" : {
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"my_buckets": {
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"composite" : {
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"sources" : [
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{
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"product": {
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"terms" : {
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"script" : {
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"source": "doc['product'].value",
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"lang": "painless"
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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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===== Histogram
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The `histogram` value source can be applied on numeric values to build fixed size
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interval over the values. The `interval` parameter defines how the numeric values should be
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transformed. For instance an `interval` set to 5 will translate any numeric values to its closest interval,
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a value of `101` would be translated to `100` which is the key for the interval between 100 and 105.
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Example:
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[source,console]
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--------------------------------------------------
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GET /_search
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{
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"aggs" : {
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"my_buckets": {
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"composite" : {
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"sources" : [
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{ "histo": { "histogram" : { "field": "price", "interval": 5 } } }
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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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The values are built from a numeric field or a script that return numerical values:
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[source,console]
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--------------------------------------------------
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GET /_search
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{
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"aggs" : {
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"my_buckets": {
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"composite" : {
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"sources" : [
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{
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"histo": {
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"histogram" : {
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"interval": 5,
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"script" : {
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"source": "doc['price'].value",
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"lang": "painless"
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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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===== Date Histogram
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The `date_histogram` is similar to the `histogram` value source except that the interval
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is specified by date/time expression:
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[source,console]
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--------------------------------------------------
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GET /_search
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{
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"aggs" : {
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"my_buckets": {
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"composite" : {
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"sources" : [
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{ "date": { "date_histogram" : { "field": "timestamp", "calendar_interval": "1d" } } }
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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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The example above creates an interval per day and translates all `timestamp` values to the start of its closest intervals.
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Available expressions for interval: `year`, `quarter`, `month`, `week`, `day`, `hour`, `minute`, `second`
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Time values can also be specified via abbreviations supported by <<time-units,time units>> parsing.
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Note that fractional time values are not supported, but you can address this by shifting to another
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time unit (e.g., `1.5h` could instead be specified as `90m`).
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*Format*
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Internally, a date is represented as a 64 bit number representing a timestamp in milliseconds-since-the-epoch.
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These timestamps are returned as the bucket keys. It is possible to return a formatted date string instead using
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the format specified with the format parameter:
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[source,console]
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--------------------------------------------------
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GET /_search
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{
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"aggs" : {
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"my_buckets": {
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"composite" : {
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"sources" : [
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{
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"date": {
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"date_histogram" : {
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"field": "timestamp",
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"calendar_interval": "1d",
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"format": "yyyy-MM-dd" <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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}
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--------------------------------------------------
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<1> Supports expressive date <<date-format-pattern,format pattern>>
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*Time Zone*
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Date-times are stored in Elasticsearch in UTC. By default, all bucketing and
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rounding is also done in UTC. The `time_zone` parameter can be used to indicate
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that bucketing should use a different time zone.
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Time zones may either be specified as an ISO 8601 UTC offset (e.g. `+01:00` or
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`-08:00`) or as a timezone id, an identifier used in the TZ database like
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`America/Los_Angeles`.
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===== Mixing different values source
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The `sources` parameter accepts an array of values source.
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It is possible to mix different values source to create composite buckets.
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For example:
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[source,console]
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--------------------------------------------------
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GET /_search
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{
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"aggs" : {
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"my_buckets": {
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"composite" : {
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"sources" : [
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{ "date": { "date_histogram": { "field": "timestamp", "calendar_interval": "1d" } } },
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{ "product": { "terms": {"field": "product" } } }
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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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This will create composite buckets from the values created by two values source, a `date_histogram` and a `terms`.
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Each bucket is composed of two values, one for each value source defined in the aggregation.
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Any type of combinations is allowed and the order in the array is preserved
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in the composite buckets.
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[source,console]
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--------------------------------------------------
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GET /_search
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{
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"aggs" : {
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"my_buckets": {
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"composite" : {
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"sources" : [
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{ "shop": { "terms": {"field": "shop" } } },
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{ "product": { "terms": { "field": "product" } } },
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{ "date": { "date_histogram": { "field": "timestamp", "calendar_interval": "1d" } } }
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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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==== Order
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By default the composite buckets are sorted by their natural ordering. Values are sorted
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in ascending order of their values. When multiple value sources are requested, the ordering is done per value
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source, the first value of the composite bucket is compared to the first value of the other composite bucket and if they are equals the
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next values in the composite bucket are used for tie-breaking. This means that the composite bucket
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`[foo, 100]` is considered smaller than `[foobar, 0]` because `foo` is considered smaller than `foobar`.
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It is possible to define the direction of the sort for each value source by setting `order` to `asc` (default value)
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or `desc` (descending order) directly in the value source definition.
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For example:
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[source,console]
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--------------------------------------------------
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GET /_search
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{
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"aggs" : {
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"my_buckets": {
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"composite" : {
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"sources" : [
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{ "date": { "date_histogram": { "field": "timestamp", "calendar_interval": "1d", "order": "desc" } } },
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{ "product": { "terms": {"field": "product", "order": "asc" } } }
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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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\... will sort the composite bucket in descending order when comparing values from the `date_histogram` source
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and in ascending order when comparing values from the `terms` source.
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==== Missing bucket
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By default documents without a value for a given source are ignored.
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It is possible to include them in the response by setting `missing_bucket` to
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`true` (defaults to `false`):
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[source,console]
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--------------------------------------------------
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GET /_search
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{
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"aggs" : {
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"my_buckets": {
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"composite" : {
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"sources" : [
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{ "product_name": { "terms" : { "field": "product", "missing_bucket": 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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In the example above the source `product_name` will emit an explicit `null` value
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for documents without a value for the field `product`.
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The `order` specified in the source dictates whether the `null` values should rank
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first (ascending order, `asc`) or last (descending order, `desc`).
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==== Size
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The `size` parameter can be set to define how many composite buckets should be returned.
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Each composite bucket is considered as a single bucket so setting a size of 10 will return the
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first 10 composite buckets created from the values source.
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The response contains the values for each composite bucket in an array containing the values extracted
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from each value source.
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==== After
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If the number of composite buckets is too high (or unknown) to be returned in a single response
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it is possible to split the retrieval in multiple requests.
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Since the composite buckets are flat by nature, the requested `size` is exactly the number of composite buckets
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that will be returned in the response (assuming that they are at least `size` composite buckets to return).
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If all composite buckets should be retrieved it is preferable to use a small size (`100` or `1000` for instance)
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and then use the `after` parameter to retrieve the next results.
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For example:
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[source,console]
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--------------------------------------------------
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GET /_search
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{
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"aggs" : {
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"my_buckets": {
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"composite" : {
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"size": 2,
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"sources" : [
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{ "date": { "date_histogram": { "field": "timestamp", "calendar_interval": "1d" } } },
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{ "product": { "terms": {"field": "product" } } }
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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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// TEST[s/_search/_search\?filter_path=aggregations/]
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\... returns:
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[source,js]
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--------------------------------------------------
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{
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...
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"aggregations": {
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"my_buckets": {
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"after_key": { <1>
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"date": 1494288000000,
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"product": "mad max"
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},
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"buckets": [
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{
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"key": {
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"date": 1494201600000,
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"product": "rocky"
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},
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"doc_count": 1
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},
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{
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"key": {
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"date": 1494288000000,
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"product": "mad max"
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},
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"doc_count": 2
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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/\.\.\.//]
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<1> The last composite bucket returned by the query.
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NOTE: The `after_key` is equals to the last bucket returned in the response before
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any filtering that could be done by <<search-aggregations-pipeline, Pipeline aggregations>>.
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If all buckets are filtered/removed by a pipeline aggregation, the `after_key` will contain
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the last bucket before filtering.
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The `after` parameter can be used to retrieve the composite buckets that are **after**
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the last composite buckets returned in a previous round.
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For the example below the last bucket can be found in `after_key` and the next
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round of result can be retrieved with:
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[source,console]
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--------------------------------------------------
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GET /_search
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{
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"aggs" : {
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"my_buckets": {
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"composite" : {
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"size": 2,
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"sources" : [
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{ "date": { "date_histogram": { "field": "timestamp", "calendar_interval": "1d", "order": "desc" } } },
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{ "product": { "terms": {"field": "product", "order": "asc" } } }
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],
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"after": { "date": 1494288000000, "product": "mad max" } <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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<1> Should restrict the aggregation to buckets that sort **after** the provided values.
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==== Sub-aggregations
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Like any `multi-bucket` aggregations the `composite` aggregation can hold sub-aggregations.
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These sub-aggregations can be used to compute other buckets or statistics on each composite bucket created by this
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parent aggregation.
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For instance the following example computes the average value of a field
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per composite bucket:
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[source,console]
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--------------------------------------------------
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GET /_search
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{
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"aggs" : {
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"my_buckets": {
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"composite" : {
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"sources" : [
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{ "date": { "date_histogram": { "field": "timestamp", "calendar_interval": "1d", "order": "desc" } } },
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{ "product": { "terms": {"field": "product" } } }
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]
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},
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"aggregations": {
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"the_avg": {
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"avg": { "field": "price" }
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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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// TEST[s/_search/_search\?filter_path=aggregations/]
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\... returns:
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[source,js]
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--------------------------------------------------
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{
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...
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"aggregations": {
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"my_buckets": {
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"after_key": {
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"date": 1494201600000,
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"product": "rocky"
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},
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"buckets": [
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{
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"key": {
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"date": 1494460800000,
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"product": "apocalypse now"
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},
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"doc_count": 1,
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"the_avg": {
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"value": 10.0
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}
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},
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{
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"key": {
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"date": 1494374400000,
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"product": "mad max"
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},
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"doc_count": 1,
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"the_avg": {
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"value": 27.0
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}
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},
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{
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"key": {
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"date": 1494288000000,
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"product" : "mad max"
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},
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"doc_count": 2,
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"the_avg": {
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"value": 22.5
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}
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},
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{
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"key": {
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"date": 1494201600000,
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"product": "rocky"
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},
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"doc_count": 1,
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"the_avg": {
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"value": 10.0
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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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// TESTRESPONSE[s/\.\.\.//]
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==== Pipeline aggregations
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The composite agg is not currently compatible with pipeline aggregations, nor does it make sense in most cases.
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E.g. due to the paging nature of composite aggs, a single logical partition (one day for example) might be spread
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over multiple pages. Since pipeline aggregations are purely post-processing on the final list of buckets,
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running something like a derivative on a composite page could lead to inaccurate results as it is only taking into
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account a "partial" result on that page.
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Pipeline aggs that are self contained to a single bucket (such as `bucket_selector`) might be supported in the future.
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