[GitHub] [spark] maropu commented on pull request #29009: [SPARK-32193][SQL] Update migrate guide docs on regexp function

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maropu commented on pull request #29009:
URL: https://github.com/apache/spark/pull/29009#issuecomment-654207971


   I get a bit confiused and Hive really supports REGEX as a function?
   ```
   // REGEXP case in hive (3.1.1)
   hive> SELECT 'abc' REGEXP '([a-z]+)';
   OK
   true
   
   hive> select REGEXP('abc','([a-z]+)');
   NoViableAltException(251@[])
        at 
org.apache.hadoop.hive.ql.parse.HiveParser_SelectClauseParser.selectClause(HiveParser_SelectClauseParser.java:962)
       ...
   FAILED: ParseException line 1:7 cannot recognize input near 'REGEXP' '(' 
''abc'' in select clause
   
   // RLIKE in hive
   hive> SELECT 'abc' RLIKE '([a-z]+)';
   OK
   true
   
   hive> select RLIKE('abc','([a-z]+)');
   NoViableAltException(265@[])
        at 
org.apache.hadoop.hive.ql.parse.HiveParser_SelectClauseParser.selectClause(HiveParser_SelectClauseParser.java:962)
        ...
   FAILED: ParseException line 1:7 cannot recognize input near 'RLIKE' '(' 
''abc'' in select clause
   
   // REGEXP in mysql
   mysql> SELECT 'abc' REGEXP '([a-z]+)';
   +-------------------------+
   | 'abc' REGEXP '([a-z]+)' |
   +-------------------------+
   |                       1 |
   +-------------------------+
   
   mysql> select REGEXP('abc','([a-z]+)');
   ERROR 1064 (42000): You have an error in your SQL syntax; check the manual 
that corresponds to your MySQL server version for the right syntax to use near 
'REGEXP('abc','([a-z]+)')' at line 1
   
   // RLIKE in mysql
   mysql> SELECT 'abc' RLIKE '([a-z]+)';
   +------------------------+
   | 'abc' RLIKE '([a-z]+)' |
   +------------------------+
   |                      1 |
   +------------------------+
   
   mysql> select RLIKE('abc','([a-z]+)');
   ERROR 1064 (42000): You have an error in your SQL syntax; check the manual 
that corresponds to your MySQL server version for the right syntax to use near 
'RLIKE('abc','([a-z]+)')' at line 1
   ```


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