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https://issues.apache.org/jira/browse/IMPALA-11355?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Kurt Deschler updated IMPALA-11355:
-----------------------------------
Priority: Critical (was: Major)
> Add STRING overloads for functions that consume time of day
> -----------------------------------------------------------
>
> Key: IMPALA-11355
> URL: https://issues.apache.org/jira/browse/IMPALA-11355
> Project: IMPALA
> Issue Type: Improvement
> Components: Backend
> Affects Versions: Impala 4.0.0
> Reporter: Csaba Ringhofer
> Assignee: Csaba Ringhofer
> Priority: Critical
>
> IMPALA-9531 dropped support for "dateless timestamps", e.g. cast("12:05:05"
> as timestamp) now returns NULL.
> This led to breaking functions like minute("12:05:05"), as minute() expects a
> timestamp, and Impala adds an implicit cast, so what actually happens is
> minute(cast("12:05:05" as timestamp)), which returns NULL. The same
> expression works in Hive and other databases like mySQL.
> IMO the best solution would be to add overloads for similar functions that
> take STRING as argument:
> - this would solve the issue above
> - would be consistent with Hive where minute() expects a STRING, not a
> TIMESTAMP
> - it would be also faster, as the string->timestamp parsing is done anyway
> during casting, and extracting the minute part of a timestamp needs an a
> large integer division
> At the first glance this should be done for the following functions:
> HOUR(TIMESTAMP ts)
> MINUTE(TIMESTAMP ts)
> SECOND(TIMESTAMP ts)
> MILLISECOND(TIMESTAMP ts)
>
> TRUNC(TIMESTAMP / DATE ts, STRING unit) would also make sense, though I am
> not sure if it ever worked with dateless timestamp (in Hive this also takes
> STRING)
> For functions like MONTH this is not needed for correctness, as we can
> convert "timeless dates" to timestamps or dates without problem. For
> performance it would still make sense to work on STRINGs directly.
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