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https://issues.apache.org/jira/browse/DRILL-6768?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16670007#comment-16670007
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Bohdan Kazydub commented on DRILL-6768:
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[~vitalii], yes, it is possible.
One way is to introduce `NullHandling.NULL_IF_NULL_OR_EMPTY_STRING` strategy,
which handles empty string input as if it was NULL.
The other way is to enhance `NullHandling.NULL_IF_NULL` (there is an open issue
for this) to allow setting null values to output from function body methods.
While there will still be a need to handle empty strings yourself there could
be less function definitions because handling framework should take care of
this cases.
> Improve to_date, to_time and to_timestamp and corresponding cast functions to
> handle empty string when `drill.exec.functions.cast_empty_string_to_null`
> option is enabled
> -------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: DRILL-6768
> URL: https://issues.apache.org/jira/browse/DRILL-6768
> Project: Apache Drill
> Issue Type: Improvement
> Affects Versions: 1.14.0
> Reporter: Bohdan Kazydub
> Assignee: Bohdan Kazydub
> Priority: Major
> Labels: doc-impacting, ready-to-commit
> Fix For: 1.15.0
>
>
> When `drill.exec.functions.cast_empty_string_to_null` option is enabled
> `to_date`, `to_time` and `to_timestamp` functions while converting string to
> according type in case if null or empty string values are passed will return
> NULL (to avoid CASE clauses which are littering a query and will work in
> accordance with their respective CAST counterparts) for both cases.
>
>
>
> CASTs will be handled in a similar way (uniformly with numeric types):
>
> ||Value to cast||Now||Will be||
> |NULL|NULL|NULL|
> |'' (empty string)|Error in many cases (except numerical types)|NULL|
> CAST empty string to null (in case of enabled option) will be supported by
> DATE, TIME, TIMESTAMP, INTERVAL YEAR, INTERVAL MONTH and INTERVAL DAY
> functions in addition to numeric types.
>
> *For documentation*
> TBA
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