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https://issues.apache.org/jira/browse/DRILL-5562?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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James Turton updated DRILL-5562:
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Fix Version/s: (was: 1.21.0)
> Vector types IntervalYear, IntervalDay and Interval are of the wrong width
> --------------------------------------------------------------------------
>
> Key: DRILL-5562
> URL: https://issues.apache.org/jira/browse/DRILL-5562
> Project: Apache Drill
> Issue Type: Bug
> Affects Versions: 1.8.0
> Reporter: Paul Rogers
> Priority: Major
>
> Drill provides three interval types, described in `ValueVectorTypes.tdd`:
> * {{IntervalYear}}: a duration in months (sic)
> * {{IntervalDay}}: a duration in days and ms.
> * {{Interval}}: a duration in months, days and ms.
> The file defines the width of each "field" (ms, days, months) as an int: 4
> bytes. But, the total vector width is wrong:
> * {{IntervalYear}}: 8 bytes (should be 4: for months)
> * {{IntervalDay}}: 12 bytes (should be 8: for days and ms.)
> * {{Interval}}: 16 bytes (should be 12: for months, days and ms.)
> It could be that the extra 4 bytes is supposed to be for a time zone. But,
> time zones don't apply to intervals: an hour is the same duration everywhere
> on earth.
> Since an interval does not contain a point in time, a time-zone is not useful
> even for daylight savings time adjustments.
> The code for each type reflects the "missing" 4 bytes. For example, for the
> 12-byte {{IntervalDay}} vector:
> {code}
> public void set(int index, int days, int milliseconds) {
> final int offsetIndex = index * VALUE_WIDTH;
> data.setInt(offsetIndex, days);
> data.setInt((offsetIndex + 4), milliseconds);
> }
> {code}
> Note also that the Drill IntervalDay need not be two fields wide. Except on a
> leap second, a day has a fixed number of milliseconds. And, the only way to
> compensate for a leap second is to know a point in time, which the interval
> does not have. Even if measured across a leap second, an interval of a minute
> is always 60 seconds. It is only when doing:
> {code}
> end date/time = start date/time + interval
> {code}
> is the leap second even needed.
> Although the ISO format expresses intervals as a tuple of (year, month, day,
> hour, minute, second), the same value can be expressed as (months, ms) (with
> the proper conversions), so Drill's interval types need only be 4 and 8 bytes
> wide.
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