# Retrieve both parent and child documents
**URL:** https://discuss.elastic.co/t/retrieve-both-parent-and-child-documents/78863
**Category:** Elasticsearch
**Created:** [March 16, 2017, 1:06pm UTC](https://discuss.elastic.co/t/retrieve-both-parent-and-child-documents/78863 "2017-03-16T13:06:20Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@Fang\_Yan](https://discuss.elastic.co/u/Fang_Yan)
#### Post date: [March 16, 2017, 1:06pm UTC](https://discuss.elastic.co/t/retrieve-both-parent-and-child-documents/78863/1 "2017-03-16T13:06:20Z")
I have a data model with parent-child relationship.
Parent type subject mapping:
{
"properties": {
"MRN": {
"type": "keyword"
},
"display\_name": {
"type": "keyword"
},
"protocols": {
"type": "keyword"
},
"gender": {
"type": "keyword"
},
"dob": {
"type": "date"
}
....
}
Child type lab mapping:
{
"\_parent": {
"type": "subject",
"eager\_global\_ordinals": false
},
"properties": {
"GUID": {
"type": "keyword"
},
"blinded": {
"type": "boolean"
},
"collect\_time": {
"type": "date"
},
.....
}
Each lab document has only 1 parent, while a subject can have many lab documents.
I want to retrieve both parent and child document so the subject's gender, dob etc can be returned as search result.
Sample query:
{"bool": {
"must": [
{
"has\_parent": {
"parent\_type": "subject",
"inner\_hits": {
"\_source": {
"includes": ["MRN", "display\_name", "gender", "race", "ethnic\_group", "dob"]
}
},
"query": {
"bool": {
"must": [
{
"terms": {
"protocols": ["18785-BTRIS-TEST-01"]
}
}
]
}
}
}
},
{
"term": {
"\_type": "lab"
}
},
{
"query\_string": {
"default\_field": "[observation.name](http://observation.name)",
"query": "glucose"
}
}
]
}}
This query gives the expected results. However, it's quite slow. (Takes about 5 seconds on my test environment for size 1000). If I remove the "inner\_hits" part, the same query run much faster (100~ milliseconds).
My question: how to retrieve both parent and child documents in a more efficient manner?
---
### Author:  [@Matthew\_Isett](https://discuss.elastic.co/u/Matthew_Isett)
#### Post date: [March 16, 2017, 2:53pm UTC](https://discuss.elastic.co/t/retrieve-both-parent-and-child-documents/78863/2 "2017-03-16T14:53:20Z")
The most efficient retrieval is de-normalize the data needed into a single object. Which you built by placing the needed ["MRN", "display\_name", "gender", "race", "ethnic\_group", "dob"] in the child document.
If you upgrade to 5.2 - you can use the Search Profiler in Dev Tools to look at the time breakouts.
---
### Author:  [@Matthew\_Isett](https://discuss.elastic.co/u/Matthew_Isett)
#### Post date: [March 28, 2017, 12:59pm UTC](https://discuss.elastic.co/t/retrieve-both-parent-and-child-documents/78863/4 "2017-03-28T12:59:39Z")
Can you test out this reverse- nested agg. See if it provides a performance increase over inner hits
[https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations-bucket-reverse-nested-aggregation.html](https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations-bucket-reverse-nested-aggregation.html)
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [April 25, 2017, 1:00pm UTC](https://discuss.elastic.co/t/retrieve-both-parent-and-child-documents/78863/5 "2017-04-25T13:00:05Z")
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