How do I convert int96 timestamps from Parquet files to Go timestamps?

Casting int96 Timestamp from Parquet to Go

When dealing with int96 timestamp values stored in Parquet files, the need arises to convert these values into timestamps within Golang applications. This issue can be encountered when working with data pipelines or analytics frameworks.

Understanding int96 Timestamp

Int96 timestamp is a 12-byte value that represents a timestamp with microsecond precision. The first 8 bytes contain the time as nanoseconds from midnight, while the last 4 bytes represent the Julian Day Number (JDN).

Conversion to Timestamp in Go

To cast an int96 timestamp to a Go timestamp, the following steps are essential:

1. Extract the Time and Date Values:

   • Split the int96 array into two parts: the time part (8 bytes) and the date part (4 bytes).

2. Reverse the Byte Order:

   • Int96 timestamps use a reverse byte order. To obtain the correct representation in Go, reverse the byte order of both the time and date parts. This ensures that the bytes are arranged in big-endian format, as Go timestamps expect.

3. Convert Time to Nanoseconds:

   • Interpret the 8 bytes of the time part as an int64 value. This represents the number of nanoseconds elapsed from midnight.

4. Convert Date to JDN:

   • Interpret the 4 bytes of the date part as a uint32 value. This represents the Julian Day Number.

5. Combine Time and Date:

   • Create a Go time.Time object by combining the time (nanoseconds) and date (JDN). This will result in a timestamp with microsecond precision.

Example Code:

To illustrate the casting process in Go, consider the following example:

import (
    "time"
)

// Convert Int96ToTimestamp converts an int96 timestamp to a Go timestamp (time.Time).
func ConvertInt96ToTimestamp(int96Bytes []byte) (time.Time, error) {
    // Extract the time and date parts.
    timeBytes := int96Bytes[:8]
    dateBytes := int96Bytes[8:]

    // Reverse the byte order.
    reverseBytes(timeBytes)
    reverseBytes(dateBytes)

    // Convert time to nanoseconds.
    timeInt64, err := Int64FromBytes(timeBytes)
    if err != nil {
        return time.Time{}, err
    }

    // Convert date to JDN.
    dateUint32, err := Uint32FromBytes(dateBytes)
    if err != nil {
        return time.Time{}, err
    }

    // Create a Go time.Time object.
    timestamp := time.Date(int(dateUint32), 1, 1, 0, 0, 0, int64(timeInt64), time.UTC)

    return timestamp, nil
}

By implementing these conversion steps, Golang applications can efficiently handle int96 timestamp values encountered in Parquet data and transform them into Go timestamps for further processing or analysis.

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