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https://issues.apache.org/jira/browse/CASSANDRA-14724?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16617326#comment-16617326
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Benjamin Lerer commented on CASSANDRA-14724:
--------------------------------------------
Lets first focus on the problem of {{DST boundaries}}.
{{Durations}} as explained
[here|http://cassandra.apache.org/doc/latest/cql/types.html#working-with-durations]
contains 3 integers which are: a number of months, a number of days and a
number of nanoseconds. This is due to the fact that the number of days in a
month can change, and a day can have 23 or 25 hours depending on the daylight
saving.
If you want to fetch all the data from the last 2 days but do not care that the
day lasted 23, 24 or 25 hours you should query the data using a query like
{{SELECT \* FROM myTable WHERE pk = `XXX` AND operationTime > ? - 2d}}. If
instead you want to fetch all the data from the last 2 hours but do not care
about the fact that during that time your time changed due to daylight saving
you should us {{SELECT \* FROM myTable WHERE pk = `XXX` AND operationTime > ? -
2h}}.
In my opinion for DST it is the correct behavior because it allows you to query
exactly the data that you want.
Leap seconds are a much more complex problem because the Java libraries does
not really handle leap seconds either. By consequence there is not much that we
can do here.
> Duration addition to Date/Timestamp is broken for leapseconds
> -------------------------------------------------------------
>
> Key: CASSANDRA-14724
> URL: https://issues.apache.org/jira/browse/CASSANDRA-14724
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Reporter: Benedict
> Assignee: Benjamin Lerer
> Priority: Major
> Labels: correctness
>
> Hours, Minutes and Seconds are not always of the same duration; it varies
> when they cross a leap second (or DST boundary). When we add durations to
> instants, we do not account for this (as we have by then lost the necessary
> information). Duration should take (and store) all components of time.
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