Android Firebase : Update/Add record in Nested Array data

Question

I am stuck in one case of firebase operation in android. My Requirement :

I have table Named : "Values" This value table contains following type of data.

  {
    "menu": [
             {
               "category": "cocktails",
               "product": [
                            {
                              "id": "123",
                              "name": "test1"
                            },
                            {
                              "id": "456",
                              "name": "test2"
                            }
                          ]
            },
            {
               "category": "vodka",
               "product": [
                            {
                               "id": "789",
                               "name": "test3"
                             },
                             {
                                "id": "901",
                                "name": "test4"
                             }
                         ]
              }
           ]
       }

Now, I want to update id : 123 with name = "test5" , How to update this nested array object in firebase database in android?

I tried following but it update/add Entire menu array not perticular product array object.

I just want to update in product array object.

Following are the code that i tried, but it update all menu array.

      val listPorduct = ArrayList<HashMap<String, Any>>()

      for ((i, product) in productList.withIndex()) {

            var productMap = HashMap<String, Any>()

              productMap = hashMapOf(
                "id" to "123",
                "name" to "test5")

             listPorduct.add(productMap)
       }

        val map = hashMapOf<String, Any>()
        map.put("category", list[position].category)
        map.put("product", listPorduct)

       repository.getTabs().update("menu", FieldValue.arrayUnion(map))

if i am try with

       repository.getTabs().update("menu/product", FieldValue.arrayUnion(map))

       or

       repository.getTabs().update("menu.product", FieldValue.arrayUnion(map))

then getting issue / or dot not allowed. i have latest firebase gradle file.

How update particular position of product object? Please anyone can help me to solve out this?

Image of firebase database.

stackoverflow.com/questions/59611061/… this is not an answer — Jenis Kasundra
– Jenis Kasundra, Commented Jan 7, 2020 at 13:47
we need to update array inside an array please give a solution for this question — Jenis Kasundra
– Jenis Kasundra, Commented Jan 7, 2020 at 13:49
@AlexMamo: While the question you linked shows a similar problem, it is often helpful for devs to see how to apply it to their own problem. I highly recommend leading a comment when closing dupes on how to apply the linked answer to their problem. I'm also not convinced the linked answer is the best answer for all cases. Storing the sub-elements in a sub-collection is a valid approach, but storing them in the same document can be valid too. I'm voting to reopen the question, allowing others to answer with the actual code of how to update the nested/array field. — Frank van Puffelen
– Frank van Puffelen, Commented Jan 7, 2020 at 14:09
@FrankvanPuffelen Ya, my bad for not leaving a comment, I usually do. Now, I just answered this question with some details regarding this specific use-case. However, storing the sub-elements in a sub-collection was just another solution besides the initial one. Thanks again puf. — Alex Mamo
– Alex Mamo, Commented Jan 7, 2020 at 14:45

Alex Mamo · Accepted Answer · 2020-01-08 11:30:07Z

4

The solution to this problem can be found in my answer from the following post:

firestore -- Add element in a field in hashmap

There is a slightly smaller difference. However, for your use-case, please note that the document that you gave us as an example contains a property named menu which is of type array. In this array, you have added some objects that contain two properties, a String property named category and an array named product. This array contains in term two other properties, one is the id and the other one is the name, both being of type String.

None of those arrays can be updated using FieldValue.arrayUnion(map). The only option that you have is to get the menu array as a list of HashMap<String, Any>. Once you have this map, you can simply iterate through it and get the desired data.

So to update the value of a property inside a Map, you should first get the map, do the changes and put it back. In the end, after you've done all the necessary changes, write the document back to Firestore.

Edit:

According to your comment:

In my case I have more than 5000 records in a list with a nested array.

It's hard to believe that you can nest 5000 elements into a single document because it might not fit since the maximum size for a document is 1 MiB (1,048,576 bytes). Please see usage and limits. So nesting 5000 objects into an array isn't a solution at all. In this case, the single solution that you have is to use a sub-collection and add each item from the array as a document. In this case, there are no limitations.

As a conclusion, the only highly scalable way to store an unknown large list of items is using documents in a collection. Array type fields do not scale for lists the are constantly growing because the items will eventually exceed that (1 MiB), which will obviously cause problems in the future.

edited Jan 8, 2020 at 11:30

answered Jan 7, 2020 at 14:28

Alex Mamo

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11 Comments

Jenis Kasundra Over a year ago

so we need to make menu array as a list of HashMap<String, Any> with changes and write back menu to document.

Jenis Kasundra Over a year ago

is there any other way to update a particular ArrayList's item within other ArrayList?

Alex Mamo Over a year ago

@JenisKasundra This is how you need to get it. If in the menu array would have been strings, then the OP could get that array as a List<String>. In that particular case, he could also use FieldValue.arrayUnion but not in this use-case.

Alex Mamo Over a year ago

@JenisKasundra There is currently no other way.

Topsy Over a year ago

@AlexMamo In My case i have more than 5000 record in list with nested array , So, for update single record out of 5000+ record, its good idea to do? Please can you more clarify with android code syntax how to achieve these? firebase is so much complex to handle large amount of data, there is no any easy way to handle it?

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