presto-main/src/main/java/io/prestosql/operator/aggregation/state/NullableLongStateSerializer.java/NullableLongStateSerializer/deserialize
class NullableLongStateSerializer:    @Override
    public void deserialize(Block block, int index, NullableLongState state)
    {
        state.setNull(false);
        state.setLong(BIGINT.getLong(block, index));
    }