This is a representation of the Firestore data model

Users (collection)
└── user123 (document; id = user ID)
    ├── DailyLogs (subcollection)
    │   └── 2023-09-13 (document, id = date)
    │       ├── activities (map)
    │       │   ├── Yoga (map)
    │       │   │   ├── sets (array)
    │       │   │   │   ├── 0 (map)
    │       │   │   │   │   ├── reps: 10
    │       │   │   │   │   ├── duration: "10 minutes"
    │       │   │   │   │   ├── weight: "5kg"
    │       │   │   │   ├── 1 (map)
    │       │   │   │   │   ├── reps: 8
    │       │   │   │   │   ├── duration: "8 minutes"
    │       │   │   │   │   ├── weight: "4kg"
    │       │   ├── Running (map)
    │       │   │   ├── ... (other attributes for running)
    │       │   └── ...
    │       ├── pains (map)
    │       │   ├── Left Hip (map)
    │       │   │   ├── pain level (int) 
    │       │   └── ...
    └── ...

Notes

1. In Firestore, collections/subcollections and documents don’t actually represent a file structure despite looking like one. So it can be possible to have subcollections without a real document as a parent. The italics in a collection in the UI indicate that the document itself doesn’t exist -