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https://issues.apache.org/jira/browse/FLINK-9970?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16656159#comment-16656159
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ASF GitHub Bot commented on FLINK-9970:
---------------------------------------
yanghua commented on a change in pull request #6432: [FLINK-9970] [table] Add
ASCII/CHR function for table/sql API
URL: https://github.com/apache/flink/pull/6432#discussion_r226515985
##########
File path:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/runtime/functions/ScalarFunctions.scala
##########
@@ -252,6 +252,17 @@ object ScalarFunctions {
regexp_extract(str, regex, 0)
}
+ /**
+ * Returns a numeric value of the leftmost character of the string str.
+ */
+ def ascii(str: String): Integer = {
+ if (str == null || str.equals("")) {
+ 0
Review comment:
OK, I can return `null`. In the Java world, Integer is an object, and
returning null is fine from a grammatical and semantic point of view. However,
when we use ascii('') as input to other operators, such as
xxxFunction(ascii('')). The subsequent effects of null and 0 are completely
different. Null may produce NPE or other behavior, while 0 is different. If you
have already considered this, then I have no problem here.
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> Add ASCII/CHR function for table/sql API
> ----------------------------------------
>
> Key: FLINK-9970
> URL: https://issues.apache.org/jira/browse/FLINK-9970
> Project: Flink
> Issue Type: Sub-task
> Components: Table API & SQL
> Reporter: vinoyang
> Assignee: vinoyang
> Priority: Minor
> Labels: pull-request-available
>
> for ASCII function :
> refer to :
> [https://dev.mysql.com/doc/refman/8.0/en/string-functions.html#function_ascii]
> for CHR function :
> This function convert ASCII code to a character,
> refer to : [https://doc.ispirer.com/sqlways/Output/SQLWays-1-071.html]
> Considering "CHAR" always is a keyword in many database, so we use "CHR"
> keyword.
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