Confusion converting DateTime<Utc> value to BigInteger for SQLite

[zebrapurring]

Hi all, I'm trying to add column timestamp for my SQLite entity where I would like:

• The Rust data type to be chrono::DateTime<chrono::Utc>
• The SQLite data type to be a 64-bit integer BIGINTEGER containing the date time value in milliseconds (UNIX time)

So far I tried the following:

#[sea_orm(primary_key, column_type = "BigInteger")]
#[serde(with = "chrono::serde::ts_milliseconds")]
pub timestamp: DateTime<Utc>,

However when I insert an entity I see the generated timestamp value is a string in format YYYY-mm-dd HH:MM:SS +00:00. How can I map the DateTime<Utc> value to milliseconds as i64 (and viceversa) when interfacing with the database?