Unable to increment value in list of object.

[harshitsinghai77]

Hey,

I have a use case where I need to increment id such as

user = {
    "...other stuff"
    "analytics": [
        {"id": increment(), "task":"task1"},
        {"id": increment(), "task":"task2"},
        {"id": increment(), "task":"task3"}
    ]
}

My code

def create_new_task(self, key: str, task: dict) -> NemoSettings:
        if not task:
            return
        task = NemoTasks(**task)
        task = task.dict()
        task["id"] = async_db.util.increment()
        new_task = {
            "tasks": async_db.util.append(task),
        }
        async_db.update(new_task, key)

But I'm getting an error saying:
TypeError: Object of type Increment is not JSON serializable
Which makes sense.

On print I get this

{'id': <deta.base.Util.Increment object at 0x7f899005ac40>, 'created_at': '2022-05-26 08:12:51.714123', 'task_description': 'My Second Task', 'duration': 3600, 'task_date': '2022-05-26 08:12:51.714125'}

What am I doing wrong here?

[jnsougata]

async_db.util.increment() this method besically returns Increment type which is not a JSON serializable data type. You should assign some value of type str or int or float or list or None to the key id to use it as json and use it with update method in async_db.

Note: Python a dict can contain custom types / objets to any key but JSON can't as it relies on generic data types. Unlike JSON python keys can be integers too.

[rohanshiva]

Hello,

Can you please clarify your situation?

If I understand it correctly, you are working with similar situation as follows:

Initially

{
  "key": "key",
  "tasks": [
    {
      "id": 1,
      "task": "wake up"
    },
    {
      "id": 2,
      "task": "eat"
    }
  ]
}

After update

{
  "key": "key",
  "tasks": [
    {
      "id": 1,
      "task": "wake up"
    },
    {
      "id": 2,
      "task": "eat"
    },
    {
      "id": 3,
      "task": "sleep"
    }
  ]
}

As far as I understand, you are dealing with a similar situation and you are trying to create a new task in the function specified.

If so, you are correct the SDK doesn't support nested increments. However, here is a simple snippet that might help you.

def get_task(task, id):
    res = {**task}
    res["id"] = id 
    return res

def create_new_task(key, task):
    item = db.get(key)
    del item["key"]

    task = get_task(task, len(item["tasks"])+1)

    updates = {"tasks": db.util.append(task)}

    db.update(updates, key)

create_new_task(key, {"task": "sleep"})

If this is your situation, here is another schema that might be better. Instead of storing all the tasks in a list, why not create another base and link them using the parent item's key.

For example, you can have a base called dates and store items like:

{"key": "parent_key", "date":"Monday, June 10, 2022"}

Now, you can have another base called tasks and store items like:

{"key":"task1", "task": "wake up", "created_at": 1653674846, "date": "parent_key"} # created_at can be a UNIX timestamp
{"key":"task2", "task": "sleep", "created_at": 1653674847, "date": "parent_key"} 

This way you can also order your tasks based on the created_at field.

[harshitsinghai77]

Hey @rohanshiva

Yes, you understood my use case correctly. I see both of your approaches, but can we not have SDK support nested increments?

This is a typical use case, NoSQL databases generally have a nested object inside a list, and these objects need increments (maybe to delete the object by id). I think when elif isinstance(value, Util.Append): payload["append"][attr] = value.val we can do an extra step and when this condition is satisfied we can again call the function with parameter, something like that. I hope you understand.

[harshitsinghai77]

Also, in your second approach, can you tell me how to reference it when querying the database to fetch all tasks by a user_id?

[rohanshiva]

@harshitsinghai77

Thank you so much for the feedback, we will look into it.

Regarding your question about querying to fetch all tasks by a user_id, you can do something like the following:

Assuming you have a base with these items:

query = {"user_id": "rohan"}
res = db.fetch(query)
all_tasks = res.items

# fetch until last is 'None'
while res.last:
    res = db.fetch(last=res.last)
    all_tasks += res.items

[harshitsinghai77]

Thanks.