Can we link documents (parent) to the documents (child)?

Elastic Stack Elasticsearch
1

I would like to know if two documents can be linked to get the search benefits?

For example:
I have a child document which is formed from parent document. I do not want to copy the complete document metadata to child so that child is searchable by parent information. If there is a way to link documents, that helps to avoid having redundant data.

I am talking in the range of Million documents here. Any information would be helpful.

Thank you

2

Have a look at Join datatype | Elasticsearch Guide [7.5] | Elastic

Why don't you want to do that?

3

Because there would be 1000's of child documents for one parent. And replicating all this duplicate data across childs is lot of space. And I am talking about Millions of parent documents and Millions of child documents.

4

But doing joins has some tradeoff.

My advice:

  • try without join, index some million documents and check if disk usage is actually a problem
  • if it's really a problem, move to parent/child but understand that it will be slower, will complicate your queries and will consume more heap space.
2 Likes
5

I was also looking for performance impact if we go this way. very helpful information. I will consider your thoughts.

6

do a virtual join by yourself with a field.
Have the parent hold the data and the child doc contains a field say "parent_id" that holds the "_id" of the parent.
That way you search with the result of the child and get the exact doc (parent) via _id.

7

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