CODEWITHSUNDEEP
elasticsearch
Kong
Kong

Reputation: 9596

Elasticsearch - equivalent of LEFT JOIN

I have 20,000,000 line items in Elasticsearch that I am happily searching (it's working amazingly well).

There is an added dimension though that I don't know how to solve:

A user can "buy" those items (in batches of 1,000 to 100,000) and I need my search to only return the items that they have not previously "bought". I'd solve this with a LEFT JOIN in SQL.

I could add a boughtBy[] field to each item, but then I would need to update lots of documents every time a user buys. Feels kind of wrong?

Upvotes: 2

Views: 5589

Answers (1)

Jakub Kotowski
Jakub Kotowski

Reputation: 7571

Elasticsearch uses Lucene which supports blockjoin. In Elasticsearch that is Parent-Child Relationships. It gives you a join but it also comes with limitations (it's no longer possible to arbitrarily distribute documents across nodes, memory requirements can explode in certain scenarios).

Elasticsearch documentation gives you a nice overview of the relationship modelling options.

If you need deep joins, more complex relationships, etc., you might consider looking into the SIREn plugin.

(disclaimer: I currently work for the company that develops SIREn)

Upvotes: 4

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