berkaysynnada opened a new pull request, #5180:
URL: https://github.com/apache/arrow-rs/pull/5180
# Which issue does this PR close?
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Closes #.
# Rationale for this change
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When intervals are compared, `IntervalDayTimeArray` and
`IntervalMonthDayNanoArray` exhibit unexpected behavior. This occurs because
they are treated as signed integers, but they require special handling since
they consist of multiple contiguous time unit blocks.
```
#[test]
fn test_interval_cmp() {
let a =
IntervalDayTimeArray::from(vec![Some(IntervalDayTimeType::make_value(0, -5))]);
let b =
IntervalDayTimeArray::from(vec![Some(IntervalDayTimeType::make_value(0, 5))]);
let res = gt(&a, &b).unwrap();
assert_eq!(&res, &BooleanArray::from(vec![ Some(false)]));
}
...
...
...
assertion `left == right` failed
left: BooleanArray
[
true,
]
right: BooleanArray
[
false,
]
```
The first unexpected behavior is observed when the LSD parts of these
intervals are negative numbers and the MSD's are 0; under these conditions,
intervals with negative values are evaluated as if they are greater than those
with positive values.
```
#[test]
fn test_interval_cmp() {
let a = IntervalMonthDayNanoArray::from(
vec![Some(IntervalMonthDayNanoType::make_value(0, -10, 0))],
);
let b = IntervalMonthDayNanoArray::from(
vec![Some(IntervalMonthDayNanoType::make_value(0, 20,0))],
);
let res = gt(&a, &b).unwrap();
assert_eq!(&res, &BooleanArray::from(vec![ Some(false)]));
}
```
This test also fails in a similar manner.
The second problem arises when comparing relative intervals, such as 1 month
and 30 days. In such cases, we can not arrive at an absolute result (e.g. days
in a month can change). Therefore, to stay on the safe side, we adopt the
following semantics: A comparison returns true if it holds certainly.
Otherwise, it returns false. Going back to our example, we return false for
both 1 month < 30 days and 1 month > 30 days. It is impossible to impose a
total order on intervals, but we can impose a consistent partial order with
this logic.
# What changes are included in this PR?
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sometimes worth providing a summary of the individual changes in this PR.
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`IntervalDayTimeArray` and `IntervalMonthDayNanoArray` are separately
handled before passing to `apply()` in `compare_op()`. They will be represented
with milliseconds and nanoseconds, respectively, as the maximum or minimum
value that the interval may correspond to.
As we need an exact representation of `IntervalMonthDayNano` in nanoseconds
to prevent overflow cases, a variant for a 128-bit signed integer in DataType
is added. Necessary extensions are accordingly implemented.
# Are there any user-facing changes?
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updated before approving the PR.
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