293 lines
6.5 KiB
Markdown
293 lines
6.5 KiB
Markdown
---
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layout: default
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title: Oversample
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nav_order: 17
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has_children: false
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parent: Search processors
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grand_parent: Search pipelines
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---
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# Oversample processor
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The `oversample` request processor multiplies the `size` parameter of the search request by a specified `sample_factor` (>= 1.0), saving the original value in the `original_size` pipeline variable. The `oversample` processor is designed to work with the [`truncate_hits` response processor]({{site.url}}{{site.baseurl}}/search-plugins/search-pipelines/truncate-hits-processor/) but may be used on its own.
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## Request fields
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The following table lists all request fields.
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Field | Data type | Description
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:--- | :--- | :---
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`sample_factor` | Float | The multiplicative factor (>= 1.0) that will be applied to the `size` parameter before processing the search request. Required.
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`context_prefix` | String | May be used to scope the `original_size` variable in order to avoid collisions. Optional.
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`tag` | String | The processor's identifier. Optional.
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`description` | String | A description of the processor. Optional.
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`ignore_failure` | Boolean | If `true`, OpenSearch [ignores any failure]({{site.url}}{{site.baseurl}}/search-plugins/search-pipelines/creating-search-pipeline/#ignoring-processor-failures) of this processor and continues to run the remaining processors in the search pipeline. Optional. Default is `false`.
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## Example
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The following example demonstrates using a search pipeline with an `oversample` processor.
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### Setup
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Create an index named `my_index` containing many documents:
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```json
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POST /_bulk
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{ "create":{"_index":"my_index","_id":1}}
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{ "doc": { "title" : "document 1" }}
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{ "create":{"_index":"my_index","_id":2}}
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{ "doc": { "title" : "document 2" }}
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{ "create":{"_index":"my_index","_id":3}}
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{ "doc": { "title" : "document 3" }}
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{ "create":{"_index":"my_index","_id":4}}
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{ "doc": { "title" : "document 4" }}
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{ "create":{"_index":"my_index","_id":5}}
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{ "doc": { "title" : "document 5" }}
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{ "create":{"_index":"my_index","_id":6}}
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{ "doc": { "title" : "document 6" }}
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{ "create":{"_index":"my_index","_id":7}}
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{ "doc": { "title" : "document 7" }}
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{ "create":{"_index":"my_index","_id":8}}
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{ "doc": { "title" : "document 8" }}
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{ "create":{"_index":"my_index","_id":9}}
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{ "doc": { "title" : "document 9" }}
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{ "create":{"_index":"my_index","_id":10}}
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{ "doc": { "title" : "document 10" }}
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```
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{% include copy-curl.html %}
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### Creating a search pipeline
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The following request creates a search pipeline named `my_pipeline` with an `oversample` request processor that requests 50% more hits than specified in `size`:
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```json
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PUT /_search/pipeline/my_pipeline
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{
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"request_processors": [
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{
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"oversample" : {
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"tag" : "oversample_1",
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"description" : "This processor will multiply `size` by 1.5.",
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"sample_factor" : 1.5
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}
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}
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]
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}
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```
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{% include copy-curl.html %}
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### Using a search pipeline
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Search for documents in `my_index` without a search pipeline:
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```json
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POST /my_index/_search
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{
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"size": 5
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}
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```
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{% include copy-curl.html %}
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The response contains five hits:
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<details open markdown="block">
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<summary>
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Response
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</summary>
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{: .text-delta}
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```json
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{
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"took" : 3,
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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" : {
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"value" : 10,
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"relation" : "eq"
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},
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"max_score" : 1.0,
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"hits" : [
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{
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"_index" : "my_index",
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"_id" : "1",
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"_score" : 1.0,
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"_source" : {
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"doc" : {
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"title" : "document 1"
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}
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}
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},
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{
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"_index" : "my_index",
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"_id" : "2",
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"_score" : 1.0,
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"_source" : {
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"doc" : {
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"title" : "document 2"
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}
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}
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},
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{
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"_index" : "my_index",
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"_id" : "3",
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"_score" : 1.0,
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"_source" : {
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"doc" : {
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"title" : "document 3"
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}
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}
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},
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{
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"_index" : "my_index",
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"_id" : "4",
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"_score" : 1.0,
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"_source" : {
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"doc" : {
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"title" : "document 4"
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}
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}
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},
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{
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"_index" : "my_index",
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"_id" : "5",
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"_score" : 1.0,
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"_source" : {
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"doc" : {
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"title" : "document 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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</details>
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To search with a pipeline, specify the pipeline name in the `search_pipeline` query parameter:
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```json
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POST /my_index/_search?search_pipeline=my_pipeline
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{
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"size": 5
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}
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```
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{% include copy-curl.html %}
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The response contains 8 documents (5 * 1.5 = 7.5, rounded up to 8):
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<details open markdown="block">
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<summary>
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Response
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</summary>
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{: .text-delta}
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```json
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{
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"took" : 13,
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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" : {
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"value" : 10,
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"relation" : "eq"
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},
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"max_score" : 1.0,
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"hits" : [
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{
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"_index" : "my_index",
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"_id" : "1",
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"_score" : 1.0,
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"_source" : {
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"doc" : {
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"title" : "document 1"
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}
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}
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},
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{
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"_index" : "my_index",
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"_id" : "2",
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"_score" : 1.0,
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"_source" : {
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"doc" : {
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"title" : "document 2"
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}
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}
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},
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{
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"_index" : "my_index",
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"_id" : "3",
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"_score" : 1.0,
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"_source" : {
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"doc" : {
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"title" : "document 3"
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}
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}
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},
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{
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"_index" : "my_index",
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"_id" : "4",
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"_score" : 1.0,
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"_source" : {
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"doc" : {
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"title" : "document 4"
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}
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}
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},
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{
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"_index" : "my_index",
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"_id" : "5",
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"_score" : 1.0,
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"_source" : {
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"doc" : {
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"title" : "document 5"
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}
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}
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},
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{
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"_index" : "my_index",
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"_id" : "6",
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"_score" : 1.0,
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"_source" : {
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"doc" : {
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"title" : "document 6"
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}
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}
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},
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{
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"_index" : "my_index",
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"_id" : "7",
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"_score" : 1.0,
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"_source" : {
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"doc" : {
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"title" : "document 7"
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}
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}
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},
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{
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"_index" : "my_index",
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"_id" : "8",
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"_score" : 1.0,
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"_source" : {
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"doc" : {
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"title" : "document 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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</details>
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