Parquet Field Display Drops Timestamp Precision

[ryzhyk]

convert_timestamp_millis_to_string and convert_timestamp_micros_to_string round the timestamp down to seconds, thus losing any fractional seconds when converting the timestamp to JSON:

arrow-rs/parquet/src/record/api.rs

Line 926 in 4f1f6e5

fn convert_timestamp_millis_to_string(value: i64) -> String {

Wouldn't it be better to print the fractional seconds in the RFC3339 format using %.3f for millis and %.6f for micros, like so:

    format!("{}", dt.format("%Y-%m-%d %H:%M:%S%.3f %:z"))

This is a simple fix, and I am happy to create a PR, but was wondering if there's any reason for the current approach, which throws away fractional seconds.

[tustvold]

Printing the real timestamp makes sense to me, but I have little context on the record (non-arrow) APIs. FWIW the arrow APIs will be significantly faster and are better supported