Function run_migrate 

pub async fn run_migrate(
    conn: &impl DbConnection,
    migrations_dir: &str,
    dialect: Dialect,
) -> Result<u32, MigrateError>

Applies pending migrations from the given directory to the database.

Migrations without a directory on the target machine — a single-binary distribution — use run_migrate_embedded instead; both share the same apply path.

Errors

Returns MigrateError on database, I/O, or hash mismatch failures.