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https://issues.apache.org/jira/browse/SPARK-47409?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Wenchen Fan resolved SPARK-47409.
---------------------------------
Fix Version/s: 4.0.0
Resolution: Fixed
Issue resolved by pull request 46206
[https://github.com/apache/spark/pull/46206]
> StringTrim & StringTrimLeft/Right/Both (binary & lowercase collation only)
> --------------------------------------------------------------------------
>
> Key: SPARK-47409
> URL: https://issues.apache.org/jira/browse/SPARK-47409
> Project: Spark
> Issue Type: Sub-task
> Components: SQL
> Affects Versions: 4.0.0
> Reporter: Uroš Bojanić
> Assignee: David Milicevic
> Priority: Major
> Labels: pull-request-available
> Fix For: 4.0.0
>
>
> Enable collation support for the *StringTrim* built-in string function in
> Spark (including {*}StringTrimBoth{*}, {*}StringTrimLeft{*},
> {*}StringTrimRight{*}). First confirm what is the expected behaviour for
> these functions when given collated strings, and then move on to
> implementation and testing. One way to go about this is to consider using
> {_}StringSearch{_}, an efficient ICU service for string matching. Implement
> the corresponding unit tests (CollationStringExpressionsSuite) and E2E tests
> (CollationSuite) to reflect how this function should be used with collation
> in SparkSQL, and feel free to use your chosen Spark SQL Editor to experiment
> with the existing functions to learn more about how they work. In addition,
> look into the possible use-cases and implementation of similar functions
> within other other open-source DBMS, such as
> [PostgreSQL|[https://www.postgresql.org/docs/]].
>
> The goal for this Jira ticket is to implement the *StringTrim* function so it
> supports binary & lowercase collation types currently supported in Spark. To
> understand what changes were introduced in order to enable full collation
> support for other existing functions in Spark, take a look at the Spark PRs
> and Jira tickets for completed tasks in this parent (for example: Contains,
> StartsWith, EndsWith).
>
> Read more about ICU [Collation Concepts|http://example.com/] and
> [Collator|http://example.com/] class, as well as _StringSearch_ using the
> [ICU user
> guide|https://unicode-org.github.io/icu/userguide/collation/string-search.html]
> and [ICU
> docs|https://unicode-org.github.io/icu-docs/apidoc/released/icu4j/com/ibm/icu/text/StringSearch.html].
> Also, refer to the Unicode Technical Standard for string
> [searching|https://www.unicode.org/reports/tr10/#Searching] and
> [collation|https://www.unicode.org/reports/tr35/tr35-collation.html#Collation_Type_Fallback].
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