Question

I know that in elasticsearch, we can have child/parent relationships between documents.

And then, when indexing, I can pass the parent id so that the child and parent documents are linked:

$ curl -XPUT localhost:9200/blogs/blog_tag/1122?parent=1111 -d '{    "tag" : "something"}'

Is there anyway to model a many to many relationship in elasticsearch?

Data is resides in a MySQL database with the following schema:

account
========
id
name
some_property

group
========
id
name
description

account_group
=============
account_id
group_id
primary_group //This is 1 or 0 depending on whether the group is the primary group for that account.

This is currently my mapping for account (please excuse the array notation, I am using Elastica in PHP to talk to my elasticsearch server):

**Mapping for account**

'name' => array(
    'type' => 'string'),

'some_property' => array(
    'type' => 'string'),

'groups' => array(
   'properties' => array(
    'id'      => array('type' => 'integer'),
    'primary' => array('type' => 'boolean')
    )
),

**Mapping for group**

'name' => array(
        'type' => 'string'),

'description'=> array(
        'type' => 'string')

The problem with this approach is that if a group is deleted from the index, I will need to go through each account and delete the group id from each account. This seems to be a bit inefficient to me. I also presume that this would not be an issue when using elasticsearch’s child/parent relationships.

Is there anyway to model many-to-many relationships in elasticsearch?

Answer 1

There’s no way to model many-to-many relationships.

The only way is to store the id of each group in each account like I have done so above.

Elasticsearch is pretty efficient, so often times, reindexing is an acceptable solution. Also, elasticsearch has the notion of documents and is not a relational storage system, so many-to-many relationships would probably never be implemented.