Interval is out of spec

[alamb]

Note: migrated from original JIRA: https://issues.apache.org/jira/browse/ARROW-11645

The DataType interval is currently implemented as a i32 or i64. However, that is incorrect and does not follow the spec.
{code:java}
// DAY_TIME - Indicates the number of elapsed days and milliseconds,
// stored as 2 contiguous 32-bit integers (8-bytes in total). Support
// of this IntervalUnit is not required for full arrow compatibility.
{code}
See [https://github.com/apache/arrow/blob/master/format/Schema.fbs]

E.g. I think that IntervalDayTimeType should be a struct(i32,i32) with a C representation or something, which is how it is defined in the spec.

This would also make it easier to read from and write to, as we do not need to transmute or bitmask the values to get the correct values.

[waitingkuo]

@alamb is it solved?

arrow-rs/arrow/src/datatypes/types.rs

Lines 99 to 103 in 7a74465

	make_type!(
	IntervalDayTimeType,
	i64,
	DataType::Interval(IntervalUnit::DayTime)
	);

arrow-rs/arrow/src/datatypes/types.rs

Lines 224 to 264 in 7a74465

	impl IntervalDayTimeType {
	/// Creates a IntervalDayTimeType::Native
	///
	/// # Arguments
	///
	/// * `days` - The number of days (+/-) represented in this interval
	/// * `millis` - The number of milliseconds (+/-) represented in this interval
	pub fn make_value(
	days: i32,
	millis: i32,
	) -> <IntervalDayTimeType as ArrowPrimitiveType>::Native {
	/*
	https://github.com/apache/arrow/blob/02c8598d264c839a5b5cf3109bfd406f3b8a6ba5/cpp/src/arrow/type.h#L1433
	struct DayMilliseconds {
	int32_t days = 0;
	int32_t milliseconds = 0;
	...
	}
	64 56 48 40 32 24 16 8 0
	+-------+-------+-------+-------+-------+-------+-------+-------+
	| days | milliseconds |
	+-------+-------+-------+-------+-------+-------+-------+-------+
	*/
	let m = millis as u64 & u32::MAX as u64;
	let d = (days as u64 & u32::MAX as u64) << 32;
	(m | d) as <IntervalDayTimeType as ArrowPrimitiveType>::Native
	}
	/// Turns a IntervalDayTimeType into a tuple of (days, milliseconds)
	///
	/// # Arguments
	///
	/// * `i` - The IntervalDayTimeType to convert
	pub fn to_parts(
	i: <IntervalDayTimeType as ArrowPrimitiveType>::Native,
	) -> (i32, i32) {
	let days = (i >> 32) as i32;
	let ms = i as i32;
	(days, ms)
	}
	}

[alamb]

I agree this issue is not tracking anything actionable anymore. Thanks for the spot @waitingkuo