102 lines
2.3 KiB
Markdown
102 lines
2.3 KiB
Markdown
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---
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layout: default
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title: Nested
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parent: Bucket aggregations
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grand_parent: Aggregations
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nav_order: 140
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---
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# Nested aggregations
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The `nested` aggregation lets you aggregate on fields inside a nested object. The `nested` type is a specialized version of the object data type that allows arrays of objects to be indexed in a way that they can be queried independently of each other
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With the `object` type, all the data is stored in the same document, so matches for a search can go across sub documents. For example, imagine a `logs` index with `pages` mapped as an `object` datatype:
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```json
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PUT logs/_doc/0
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{
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"response": "200",
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"pages": [
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{
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"page": "landing",
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"load_time": 200
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},
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{
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"page": "blog",
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"load_time": 500
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}
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]
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}
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```
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OpenSearch merges all sub-properties of the entity relations that looks something like this:
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```json
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{
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"logs": {
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"pages": ["landing", "blog"],
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"load_time": ["200", "500"]
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}
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}
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```
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So, if you wanted to search this index with `pages=landing` and `load_time=500`, this document matches the criteria even though the `load_time` value for landing is 200.
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If you want to make sure such cross-object matches don’t happen, map the field as a `nested` type:
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```json
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PUT logs
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{
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"mappings": {
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"properties": {
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"pages": {
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"type": "nested",
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"properties": {
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"page": { "type": "text" },
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"load_time": { "type": "double" }
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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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Nested documents allow you to index the same JSON document but will keep your pages in separate Lucene documents, making only searches like `pages=landing` and `load_time=200` return the expected result. Internally, nested objects index each object in the array as a separate hidden document, meaning that each nested object can be queried independently of the others.
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You have to specify a nested path relative to parent that contains the nested documents:
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```json
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GET logs/_search
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{
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"query": {
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"match": { "response": "200" }
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},
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"aggs": {
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"pages": {
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"nested": {
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"path": "pages"
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},
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"aggs": {
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"min_load_time": { "min": { "field": "pages.load_time" } }
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}
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}
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}
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}
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```
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#### Example response
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```json
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...
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"aggregations" : {
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"pages" : {
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"doc_count" : 2,
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"min_price" : {
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"value" : 200.0
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}
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}
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}
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}
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```
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