Question 119081 in Firebase Question posted in
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Firebase – How to Retrieve Firestore Documents with a Specific Hashmap Field Value?

--- Users (Collection)
    |
    --- p0A1fXH4l2TpvGE2lo0x
        |
        --- List (HashMap)
            |
            --- ID (String) (Value: UQx4CWRgnVLOdKEY3AKJ)
            --- NAME (String) (Value: ...)

In Firestore, how can I find the documents that have a list ID equal to UQx4CWRgnVLOdKEY3AKJ? Before deleting the list, I need to remove it from the users who have used it. How can I determine which documents are using this list ID so I can delete them?

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2

Answers


  1. 0

    It looks like your List (HashMap) may have multiple child objects, and you want to search across all of those for a specific ID value.

    There is no way to search across all objects in a map field in Firestore. If you want to search across all ID values, add an additional array field with just this values, e.g.

    ListIDs: ["UQx4CWRgnVLOdKEY3AKJ", ...]

    With that field in place, you can then use the array-contains operator to query for matching documents.

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  2. 0

    If I understand correctly, the List field inside the user document is a Map which contains only String values. So if your database schema looks exactly like this:

    db
|
--- Users (collection)
     |
     --- $uid (document)
          |
          --- List (map) //👈
               |
               --- ID: "UQx4CWRgnVLOdKEY3AKJ"
               |
               --- NAME: "Taha Sami"

    To get all users where the ID field within the List holds the value of UQx4CWRgnVLOdKEY3AKJ, a query like this will do the trick:

    Query queryByListId = db.collection("Users").whereEqualTo("List.ID", "UQx4CWRgnVLOdKEY3AKJ");
//                                                            👆
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