345 lines
8.5 KiB
Plaintext
345 lines
8.5 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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{
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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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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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{
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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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An example of an answer typed document:
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[source,js]
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--------------------------------------------------
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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 your 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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--------------------------------------------------
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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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{
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"aggs": {
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"top-tags": {
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"terms": {
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"field": "tags",
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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",
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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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<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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"aggregations": {
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"top-tags": {
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"buckets": [
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{
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"key": "windows-server-2003",
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"doc_count": 25365, <1>
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"to-answers": {
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"doc_count": 36004, <2>
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"top-names": {
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"buckets": [
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{
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"key": "Sam",
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"doc_count": 274
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},
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{
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"key": "chris",
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"doc_count": 19
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},
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{
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"key": "david",
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"doc_count": 14
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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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"key": "linux",
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"doc_count": 18342,
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"to-answers": {
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"doc_count": 6655,
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"top-names": {
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"buckets": [
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{
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"key": "abrams",
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"doc_count": 25
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},
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{
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"key": "ignacio",
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"doc_count": 25
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},
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{
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"key": "vazquez",
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"doc_count": 25
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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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"key": "windows",
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"doc_count": 18119,
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"to-answers": {
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"doc_count": 24051,
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"top-names": {
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"buckets": [
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{
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"key": "molly7244",
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"doc_count": 265
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},
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{
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"key": "david",
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"doc_count": 27
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},
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{
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"key": "chris",
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"doc_count": 26
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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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"key": "osx",
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"doc_count": 10971,
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"to-answers": {
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"doc_count": 5902,
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"top-names": {
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"buckets": [
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{
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"key": "diago",
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"doc_count": 4
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},
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{
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"key": "albert",
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"doc_count": 3
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},
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{
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"key": "asmus",
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"doc_count": 3
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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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"key": "ubuntu",
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"doc_count": 8743,
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"to-answers": {
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"doc_count": 8784,
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"top-names": {
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"buckets": [
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{
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"key": "ignacio",
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"doc_count": 9
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},
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{
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"key": "abrams",
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"doc_count": 8
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},
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{
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"key": "molly7244",
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"doc_count": 8
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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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"key": "windows-xp",
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"doc_count": 7517,
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"to-answers": {
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"doc_count": 13610,
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"top-names": {
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"buckets": [
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{
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"key": "molly7244",
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"doc_count": 232
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},
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{
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"key": "chris",
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"doc_count": 9
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},
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{
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"key": "john",
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"doc_count": 9
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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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"key": "networking",
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"doc_count": 6739,
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"to-answers": {
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"doc_count": 2076,
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"top-names": {
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"buckets": [
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{
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"key": "molly7244",
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"doc_count": 6
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},
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{
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"key": "alnitak",
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"doc_count": 5
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},
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{
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"key": "chris",
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"doc_count": 3
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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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"key": "mac",
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"doc_count": 5590,
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"to-answers": {
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"doc_count": 999,
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"top-names": {
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"buckets": [
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{
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"key": "abrams",
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"doc_count": 2
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},
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{
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"key": "ignacio",
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"doc_count": 2
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},
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{
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"key": "vazquez",
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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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{
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"key": "wireless-networking",
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"doc_count": 4409,
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"to-answers": {
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"doc_count": 6497,
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"top-names": {
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"buckets": [
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{
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"key": "molly7244",
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"doc_count": 61
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},
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{
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"key": "chris",
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"doc_count": 5
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},
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{
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"key": "mike",
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"doc_count": 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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{
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"key": "windows-8",
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"doc_count": 3601,
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"to-answers": {
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"doc_count": 4263,
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"top-names": {
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"buckets": [
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{
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"key": "molly7244",
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"doc_count": 3
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},
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{
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"key": "msft",
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"doc_count": 2
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},
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{
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"key": "user172132",
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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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]
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}
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}
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}
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--------------------------------------------------
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<1> The number of question documents with the tag `windows-server-2003`.
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<2> The number of answer documents that are related to question documents with the tag `windows-server-2003`.
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