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https://issues.apache.org/jira/browse/FLINK-21622?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17302549#comment-17302549
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Timo Walther commented on FLINK-21622:
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[~Leonard Xu] just for your information, it is way easier nowadays to introduce
a new built-in function using the new stack.
Adding a built-in function requires changes in only 2 classes:
{{BuiltInFunctionDefinitions}} for the definition and the class that contains
the actual runtime logic.
Tests should be added in {{org.apache.flink.table.planner.functions}}.
See the reference implementation of the IFNULL function here:
[https://github.com/apache/flink/commit/df46f8948279d1ed89d7113919b4c4f720cf4199]
We should not introduce more legacy classes such as `PlannerExpressions`. Also
the new `FunctionTestBase` allows to validate input and output types properly.
> Introduce function TO_TIMESTAMP_LTZ(numeric [, precision])
> -----------------------------------------------------------
>
> Key: FLINK-21622
> URL: https://issues.apache.org/jira/browse/FLINK-21622
> Project: Flink
> Issue Type: Sub-task
> Components: Table SQL / API, Table SQL / Planner
> Reporter: Leonard Xu
> Assignee: Leonard Xu
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.13.0
>
>
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