198 lines
5.3 KiB
Plaintext
198 lines
5.3 KiB
Plaintext
[[search-aggregations-bucket-children-aggregation]]
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=== Children Aggregation
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A special single bucket aggregation that enables aggregating from buckets on parent document types to buckets on child documents.
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This aggregation relies on the <<mapping-parent-field,_parent field>> in the mapping. This aggregation has a single option:
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* `type` - The what child type the buckets in the parent space should be mapped to.
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For example, let's say we have an index of questions and answers. The answer type has the following `_parent` field in the mapping:
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[source,js]
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--------------------------------------------------
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PUT child_example
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{
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"mappings": {
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"answer" : {
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"_parent" : {
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"type" : "question"
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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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The question typed document contain a tag field and the answer typed documents contain an owner field. With the `children`
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aggregation the tag buckets can be mapped to the owner buckets in a single request even though the two fields exist in
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two different kinds of documents.
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An example of a question typed document:
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[source,js]
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--------------------------------------------------
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PUT child_example/question/1
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{
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"body": "<p>I have Windows 2003 server and i bought a new Windows 2008 server...",
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"title": "Whats the best way to file transfer my site from server to a newer one?",
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"tags": [
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"windows-server-2003",
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"windows-server-2008",
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"file-transfer"
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]
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}
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--------------------------------------------------
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// CONSOLE
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// TEST[continued]
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Examples of `answer` typed documents:
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[source,js]
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--------------------------------------------------
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PUT child_example/answer/1?parent=1&refresh
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{
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"owner": {
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"location": "Norfolk, United Kingdom",
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"display_name": "Sam",
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"id": 48
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},
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"body": "<p>Unfortunately you're pretty much limited to FTP...",
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"creation_date": "2009-05-04T13:45:37.030"
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}
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PUT child_example/answer/2?parent=1&refresh
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{
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"owner": {
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"location": "Norfolk, United Kingdom",
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"display_name": "Troll",
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"id": 49
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},
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"body": "<p>Use Linux...",
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"creation_date": "2009-05-05T13:45:37.030"
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}
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--------------------------------------------------
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// CONSOLE
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// TEST[continued]
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The following request can be built that connects the two together:
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[source,js]
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--------------------------------------------------
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POST child_example/_search?size=0
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{
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"aggs": {
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"top-tags": {
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"terms": {
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"field": "tags.keyword",
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"size": 10
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},
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"aggs": {
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"to-answers": {
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"children": {
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"type" : "answer" <1>
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},
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"aggs": {
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"top-names": {
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"terms": {
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"field": "owner.display_name.keyword",
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"size": 10
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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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// CONSOLE
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// TEST[continued]
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<1> The `type` points to type / mapping with the name `answer`.
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The above example returns the top question tags and per tag the top answer owners.
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Possible response:
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[source,js]
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--------------------------------------------------
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{
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"timed_out": false,
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"took": 25,
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"_shards": { "total": 5, "successful": 5, "failed": 0 },
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"hits": { "total": 3, "max_score": 0.0, hits: [] },
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"aggregations": {
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"top-tags": {
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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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"key": "file-transfer",
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"doc_count": 1, <1>
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"to-answers": {
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"doc_count": 2, <2>
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"top-names": {
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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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"key": "Sam",
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"doc_count": 1
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},
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{
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"key": "Troll",
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"doc_count": 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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"key": "windows-server-2003",
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"doc_count": 1, <1>
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"to-answers": {
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"doc_count": 2, <2>
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"top-names": {
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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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"key": "Sam",
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"doc_count": 1
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},
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{
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"key": "Troll",
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"doc_count": 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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"key": "windows-server-2008",
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"doc_count": 1, <1>
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"to-answers": {
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"doc_count": 2, <2>
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"top-names": {
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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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"key": "Sam",
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"doc_count": 1
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},
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{
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"key": "Troll",
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"doc_count": 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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--------------------------------------------------
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// TESTRESPONSE[s/"took": 25/"took": $body.took/]
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<1> The number of question documents with the tag `file-transfer`, `windows-server-2003`, etc.
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<2> The number of answer documents that are related to question documents with the tag `file-transfer`, `windows-server-2003`, etc.
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