Oliver Dixon
Sep 2, 2018 · 1 min read

I guess a good example would be.

Say for instant messaging.

Image a collection of ‘threads’
You might want to have a sub-collection of ‘messages’ in here because this is going to give you a lot more power when it comes to sorting/security rules/limiting/ordering while querying Firestore.

The performance would be so good if you were comparing every single thread for sub key values like ‘thread/{uid}/messages.timeCreated’ would go over threads not just messages.

In this case ‘thread/{uid}/messages.timeCreated’ would use the power of the sub collection. (Sub collection not meaning JUST an object of keys but actually a full document within the document)

Correct me if I sound like a buffoon.

    Oliver Dixon

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