Calculating size of Google Firestore documents

Question

Firestore docs give details of how to manually calculate the stored size of a document, but there does not seem to be a function provided for this on any of document reference, snapshot, or metadata.

Before I attempt to use my own calculation, does anyone know of an official or unofficial function for this?

Here is my (completely untested) first cut for such a function from my interpretation of the docs at https://firebase.google.com/docs/firestore/storage-size

function calcFirestoreDocSize(collectionName, docId, docObject) {
    let docNameSize = encodedLength(collectionName) + 1 + 16
    let docIdType = typeof(docId)
    if(docIdType === 'string') {
        docNameSize += encodedLength(docId) + 1
    } else {
        docNameSize += 8
    }  
    let docSize = docNameSize + calcObjSize(docObject)

    return  docSize
}
function encodedLength(str) {
    var len = str.length;
    for (let i = str.length - 1; i >= 0; i--) {
        var code = str.charCodeAt(i);
        if (code > 0x7f && code <= 0x7ff) {
            len++;
        } else if (code > 0x7ff && code <= 0xffff) {
            len += 2;
        } if (code >= 0xDC00 && code <= 0xDFFF) {
            i--;
        }
    }
    return len;
}

function calcObjSize(obj) {
    let key;
    let size = 0;
    let type = typeof obj;

    if(!obj) {
        return 1
    } else if(type === 'number') {
        return 8
    } else if(type === 'string') {
        return encodedLength(obj) + 1
    } else if(type === 'boolean') {
        return 1
    } else if (obj instanceof Date) {
        return 8
    } else if(obj instanceof Array) {
        for(let i = 0; i < obj.length; i++) {
            size += calcObjSize(obj[i])
        }
        return size
    } else if(type === 'object') {

        for(key of Object.keys(obj)) {
            size += encodedLength(key) + 1 
            size += calcObjSize(obj[key])
        }
        return size += 32
    }
}

Answer 1

In Android, if you want to check the size of a document against the maximum of 1 MiB (1,048,576 bytes), there is a library that can help you with that:

• https://github.com/alexmamo/FirestoreDocument-Android/tree/master/firestore-document

In this way, you'll be able to always stay below the limit. The algorithm behind this library is the one that is explained in the official documentation regarding the Storage Size.