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https://issues.apache.org/jira/browse/FLINK-3498?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15174057#comment-15174057
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ASF GitHub Bot commented on FLINK-3498:
---------------------------------------
Github user twalthr commented on a diff in the pull request:
https://github.com/apache/flink/pull/1747#discussion_r54601133
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/api/table/codegen/calls/ScalarFunctions.scala
---
@@ -49,6 +49,11 @@ object ScalarFunctions {
STRING_TYPE_INFO,
BuiltInMethod.SUBSTRING.method)
+ addSqlFunctionTrim(
--- End diff --
`TRIM` is a special case because the runtime function takes other
parameters than the user can provide. In SQL `TRIM` has its own syntax
`TRIM(BOTH '.' FROM str)`. `BOTH` is translated into a SQL Symbol but the
runtime function uses two boolean arguments. That's why we cannot pass the
arguments directly to runtime function and need a special `TrimCallGenerator`.
The SQL Symbol is translated to an integer value (the same same value can also
come from Expression API) and is then translated to the two `boolean`
parameters.
> Implement TRIM, SUBSTRING as reference design for Table API
> -----------------------------------------------------------
>
> Key: FLINK-3498
> URL: https://issues.apache.org/jira/browse/FLINK-3498
> Project: Flink
> Issue Type: Sub-task
> Components: Table API
> Reporter: Timo Walther
> Assignee: Timo Walther
>
> As described in FLINK-3497 TRIM and SUBSTRING are the first scalar functions
> implemented in Calcite and used in Table API.
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