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https://issues.apache.org/jira/browse/FLINK-13741?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16908727#comment-16908727
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Rui Li commented on FLINK-13741:
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+1 to include built-in functions for {{SHOW FUNCTIONS}}. On the other hand,
maybe it also makes sense to provide a method for users to only list
user-defined functions?
> "SHOW FUNCTIONS" should include Flink built-in functions' names
> ---------------------------------------------------------------
>
> Key: FLINK-13741
> URL: https://issues.apache.org/jira/browse/FLINK-13741
> Project: Flink
> Issue Type: Bug
> Components: Table SQL / API
> Affects Versions: 1.9.0
> Reporter: Bowen Li
> Assignee: Bowen Li
> Priority: Critical
> Labels: pull-request-available
> Fix For: 1.10.0
>
> Time Spent: 10m
> Remaining Estimate: 0h
>
> Currently "SHOW FUNCTIONS;" only returns catalog functions and
> FunctionDefinitions registered in memory, but does not include Flink built-in
> functions' names.
> AFAIK, it's standard for "SHOW FUNCTIONS;" to show all available functions
> for use in queries in SQL systems like Hive, Presto, Teradata, etc, thus it
> includes built-in functions naturally. Besides,
> {{FunctionCatalog.lookupFunction(name)}} resolves calls to built-in
> functions, it's not feeling right to not displaying functions but can
> successfully resolve to them.
> It seems to me that the root cause is the call stack for "SHOW FUNCTIONS;"
> has been a bit messy - it calls {{tEnv.listUserDefinedFunctions()}} which
> further calls {{FunctionCatalog.getUserDefinedFunctions()}}, and I'm not sure
> what's the intention of those two APIs. Are they dedicated to getting all
> functions, or just user defined functions excluding built-in ones?
> In the end, I believe "SHOW FUNCTIONS;" should display built-in functions. To
> achieve that, we either need to modify and/or rename existing APIs mentioned
> above, or add new APIs to return all functions from FunctionCatalog.
> cc [~xuefuz] [~lirui] [~twalthr]
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