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https://issues.apache.org/jira/browse/CALCITE-2571?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17455969#comment-17455969
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Julian Hyde commented on CALCITE-2571:
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This change added an {{allowExtendedTrim}} method to {{RelDataTypeSystemImpl}}
and an anonymous derived class in {{SqlTestFactory}} but as far as I can tell
those methods are never called. (Probably my mistake: as I was adding plumbing
to {{SqlConformance}} I forgot to remove all the old plumbing.) I am going to
remove those methods in CALCITE-4885.
The {{allowExtendedTrim}} method in {{SqlConformance}} is used, and is in fact
crucial to this feature, and I'm not going to touch that.
> TRIM does not match the behavior of most SQL implementations
> ------------------------------------------------------------
>
> Key: CALCITE-2571
> URL: https://issues.apache.org/jira/browse/CALCITE-2571
> Project: Calcite
> Issue Type: Bug
> Components: core
> Reporter: Andrew Pilloud
> Assignee: Julian Hyde
> Priority: Major
> Fix For: 1.18.0
>
>
> Most SQL implementations trim all characters if more then one is provided to
> the trim function. Calcite's SqlFunctions implementation silently drops the
> extra characters, resulting in data corruption.
> Here is a sampling of implementations that trim all characters:
> MySQL -
> https://dev.mysql.com/doc/refman/8.0/en/string-functions.html#function_trim
> Sql Server -
> https://docs.microsoft.com/en-us/sql/t-sql/functions/trim-transact-sql?view=sql-server-2017
> Flink -
> https://ci.apache.org/projects/flink/flink-docs-stable/dev/table/sql.html
> Spark - https://spark.apache.org/docs/2.3.0/api/sql/index.html#trim
> Postgres - https://www.postgresql.org/docs/9.1/static/functions-string.html
> SqLite - https://www.sqlite.org/lang_corefunc.html#trim
> Also see: CALCITE-2530 BEAM-4704
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