[jira] [Commented] (CASSANDRA-9229) Add functions to convert timeuuid to date or time

["Robert Stupp (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-9229?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14536361#comment-14536361 ] 

Robert Stupp commented on CASSANDRA-9229:
-----------------------------------------

[~JoshuaMcKenzie] the point why I'd prefer not to add any {{toTime}} conversion is that we only ”know” UTC - so we could only convert to UTC, which is usually wrong. You need date+time *and* time-zone to perform a correct to-time-conversion, since time zones or its definitions (e.g. daylight-saving-time) may change. Having a distributed system with probably multiple JRE versions can cause different results. Having that said, I'd like to leave any time-conversion up to the client.

> Add functions to convert timeuuid to date or time
> -------------------------------------------------
>
>                 Key: CASSANDRA-9229
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9229
>             Project: Cassandra
>          Issue Type: New Feature
>            Reporter: Michaël Figuière
>            Assignee: Benjamin Lerer
>              Labels: cql, doc-impacting
>             Fix For: 3.x
>
>         Attachments: CASSANDRA-9229.txt
>
>
> As CASSANDRA-7523 brings the {{date}} and {{time}} native types to Cassandra, it would be useful to add builtin function to convert {{timeuuid}} to these two new types, just like {{dateOf()}} is doing for timestamps.
> {{timeOf()}} would extract the time component from a {{timeuuid}}. Example use case could be at insert time with for instance {{timeOf(now())}}, as well as at read time to compare the time component of a {{timeuuid}} column in a {{WHERE}} clause.
> The use cases would be similar for {{date}} but the solution is slightly less obvious, as in a perfect world we would want {{dateOf()}} to convert to {{date}} and {{timestampOf()}} for {{timestamp}}, unfortunately {{dateOf()}} already exist and convert to a {{timestamp}}, not a {{date}}. Making this change would break many existing CQL queries which is not acceptable. Therefore we could use a different name formatting logic such as {{toDate}} or {{dateFrom}}. We could then also consider using this new name convention for the 3 dates related types and just have {{dateOf}} becoming a deprecated alias.



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