How to get a Firestore document size?

Question

From Firestore docs, we get that the maximum size for a Firestore document is:

Maximum size for a document 1 MiB (1,

Answer 1

I was looking in the Firebase reference expecting the metadata would have an attribute, but it doesn't. You can check it here.

So my next approach would be to figure the weight of the object as an approximation. The sizeOf library seems to have a reasonable API for it.

So it would be something like:

sizeof.sizeof(doc.data());

I wouldn't use the document snapshot, because it contains metadata, like if there are pending saves. On another hand overestimating could be better in some cases.

[UPDATE] Thanks to Doug Stevenson for the wonderful insight

So I was curious how much the difference would actually be, so with my clunky js I made a dirty comparison, you can see the demo here

Considering this object:

 {
  "boolean": true,
  "number": 1,
  "text": "example"
  }

And discounting the id this is the result:

| Method  | Bytes |
|---------|-------|
| FireDoc | 37    |
| sizeOf  | 64    |

So sizeOf library could be a good predictor if we want to overestimate (assuming calculations are fine and will behave more or less equal for more complex entities). But as explained in the comment, it is a rough estimation.