async function (context, arg) {
    var uid = auth.parseAuthToken(arg.token).uid;
    var hash = arg.hash;
    var device_id = arg.device_id;

    let connection = await savedb.getConnection();
    try {
        let [hash_row] = await connection.execute("SELECT hash, device_id, ref FROM users WHERE uid=?", [uid]);

        if (hash_row && hash_row.length > 0) {
            let stored = hash_row[0];
            let stored_hash = stored.hash;
            if (hash == stored_hash) {
                return {
                    status: "not_modified",
                    device_id: stored.device_id,
                    hash: stored_hash
                };
            } else if (stored.device_id == device_id) {
                return {
                    status: "same_device",
                    device_id: stored.device_id,
                    hash: stored_hash
                };
            } else {
                let [[data]] = await connection.execute("SELECT data FROM blobs WHERE id=? AND hash=?", [stored.ref, stored.hash]);
                if ( data ) {
                    return {
                        status: "ok",
                        data: data.data.toString(),
                        device_id: stored.device_id,
                        hash: stored_hash
                    };
                } else {
                    throw new j15.ApiError("corrupted_data", "Data for the user is either concurrently accessed, or corrupted");
                }
            }
        } else {
            return null;
        }
    } finally {
        connection.release();
    }
}