Elasticsearch Alternate of Join query

Question

Since we can't do joins in Elastic search.. what will be the alternate way to have join concept in Elasticsearch. An example would be grate. Like if user table has user_role with id and user details is saved in user_role table against that Id so how can I make Alternate(Join) in ES.

Thanks.

Possible duplicate of [Join query in ElasticSearch](https://stackoverflow.com/questions/22611049/join-query-in-elasticsearch) — Mišo, May 01 '19 at 09:42

score 1 · Answer 1 · answered Jan 08 '19 at 08:03

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There are few ways to overcome this. Either:

use Parent-Child Relationship In order to correlate the docs
use Nested docs. This is actually like flattening/ normalising the data such that each doc contains the user_role data.
More complex, you can move the smaller data set (for example the users roles) to be in-memory on the searching service/app, and then enrich & filter responses coming from elasticsearch with the users roles in memory while scanning the responses. This can only work if one of the joined data sets is small enough to be in memory.

answered Jan 08 '19 at 08:03

Opster Elasticsearch Expert

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Or number 4 (and the most preferred way!!): Change your data model – Byron Voorbach Jan 08 '19 at 13:00
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Totaly agree Byron. And if that's not possible and the data model require join , there's also number 5:use a relational DB, or one that supports joins. – Opster Elasticsearch Expert Jan 08 '19 at 16:36
@ByronVoorbach how can I change data model? – Ali Abdullah Jan 09 '19 at 04:42
@AliAbdullah Do you already have some in ES? Maybe you could show an example of what you have :) – Byron Voorbach Jan 09 '19 at 20:39

Elasticsearch Alternate of Join query

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