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I have a firestore collection with many document and all these documents include an array field (called "notFor") with a list of uid. In some cases the array contains only 1 value in some other cases it contains more than 1 value. Example

docA

  • notFor: "userB", "userC"

docB

  • notFor: "userB"

docC

  • notFor: "userA", "userC"

Is there any suggestion on how I could find a document in that collection that does not include "userB"? I basically would like to find docB by excluding all the docs where userC is present

I am writing in flutter however this is not so relevant for this case, I am just interested to understand if I can do something like this with the firestore operators.

thanks!

M4trix Dev
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  • I confirm this is a hard-constraint from `Firebase`: You cannot query arrays in `Firestore` based on `values` **they don't include**. It is not possible in Firestore. Now, some potential workaround that may or may not work for your specific case: **Option1:** Change your field `notFor` into a new field `for`. This way you can query using arrayContains. Now, you will have the list of authorized users only (This worked well for my project) **Option2:** Query all values then perform your filter locally on client-side. I understand this is not suitable in most use cases. – Canada2000 Oct 22 '21 at 19:36
  • Hey may thanks. I was already looking into opinion 1. My only problem is that the list of user in the notFor group is small while the ones in the “for” is very large (thousands) so I would write thousands of records. Option 2 is not good because it would increase my cost with firebase since I would need to download all the data and then filter it – M4trix Dev Oct 23 '21 at 21:30

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