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This commit changes the default out-of-the-box configuration for the number of shards from five to one. We think this will help address a common problem of oversharding. For users with time-based indices that need a different default, this can be managed with index templates. For users with non-time-based indices that find they need to re-shard with the split API in place they no longer need to resort only to reindexing. Since this has the impact of changing the default number of shards used in REST tests, we want to ensure that we still have coverage for issues that could arise from multiple shards. As such, we randomize (rarely) the default number of shards in REST tests to two. This is managed via a global index template. However, some tests check the templates that are in the cluster state during the test. Since this template is randomly there, we need a way for tests to skip adding the template used to set the number of shards to two. For this we add the default_shards feature skip. To avoid having to write our docs in a complicated way because sometimes they might be behind one shard, and sometimes they might be behind two shards we apply the default_shards feature skip to all docs tests. That is, these tests will always run with the default number of shards (one).
227 lines
5.4 KiB
Plaintext
227 lines
5.4 KiB
Plaintext
[[search-aggregations-bucket-children-aggregation]]
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=== Children Aggregation
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A special single bucket aggregation that selects child documents that have the specified type, as defined in a <<parent-join,`join` field>>.
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This aggregation has a single option:
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* `type` - The child type that should be selected.
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For example, let's say we have an index of questions and answers. The answer type has the following `join` 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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"_doc": {
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"properties": {
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"join": {
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"type": "join",
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"relations": {
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"question": "answer"
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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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The `question` document contain a tag field and the `answer` 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 document:
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[source,js]
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--------------------------------------------------
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PUT child_example/_doc/1
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{
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"join": {
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"name": "question"
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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` documents:
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[source,js]
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--------------------------------------------------
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PUT child_example/_doc/2?routing=1
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{
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"join": {
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"name": "answer",
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"parent": "1"
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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/_doc/3?routing=1&refresh
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{
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"join": {
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"name": "answer",
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"parent": "1"
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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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"took": 25,
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"timed_out": false,
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"_shards": {
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"total": 1,
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"successful": 1,
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"skipped" : 0,
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"failed": 0
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},
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"hits": {
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"total": 3,
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"max_score": 0.0,
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"hits": []
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},
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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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