[GitHub] spark pull request #17655: [SPARK-20156] [SQL] [FOLLOW-UP] Java String toLow...

[HyukjinKwon]

Github user HyukjinKwon commented on a diff in the pull request:

    https://github.com/apache/spark/pull/17655#discussion_r111852553
  
    --- Diff: 
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/SessionCatalog.scala
 ---
    @@ -114,14 +114,14 @@ class SessionCatalog(
        * Format table name, taking into account case sensitivity.
        */
       protected[this] def formatTableName(name: String): String = {
    -    if (conf.caseSensitiveAnalysis) name else name.toLowerCase
    +    if (conf.caseSensitiveAnalysis) name else name.toLowerCase(Locale.ROOT)
    --- End diff --
    
    I don't think column names have such restrictions. Assuming 
https://github.com/apache/spark/pull/7165, it seems we support other characters 
in column names. I can provide several cases that data becomes column names as 
below:
    
    ```scala
    scala> Seq("아").toDF("a").groupBy("a").pivot("a").count().show()
    +---+---+
    |  a|  아|
    +---+---+
    |  아|  1|
    +---+---+
    ```
    
    ```scala
    scala> import org.apache.spark.sql.functions
    import org.apache.spark.sql.functions
    
    scala> spark.range(1).select(functions.lit("아")).show()
    +---+
    |  아|
    +---+
    |  아|
    +---+
    ```
    
    Seems parser does not allow such characters though.
    
    ```sql
    scala> sql("SELECT 아 FROM tbl")
    org.apache.spark.sql.catalyst.parser.ParseException:
    no viable alternative at input 'SELECT 아'(line 1, pos 7)
    
    == SQL ==
    SELECT 아 FROM tbl
    -------^^^
    
      at 
org.apache.spark.sql.catalyst.parser.ParseException.withCommand(ParseDriver.scala:210)
      at 
org.apache.spark.sql.catalyst.parser.AbstractSqlParser.parse(ParseDriver.scala:112)
      at 
org.apache.spark.sql.execution.SparkSqlParser.parse(SparkSqlParser.scala:48)
      at 
org.apache.spark.sql.catalyst.parser.AbstractSqlParser.parsePlan(ParseDriver.scala:66)
      at org.apache.spark.sql.SparkSession.sql(SparkSession.scala:622)
      ... 48 elided
    ```
    
    It seems we can still select
    
    ```scala
    scala> 
Seq("아").toDF("a").groupBy("a").pivot("a").count().createOrReplaceTempView("tbl")
    
    scala> sql("SELECT *FROM tbl").show()
    +---+---+
    |  a|  아|
    +---+---+
    |  아|  1|
    +---+---+
    ```
    
    If these were mistakenly supported, these should have the restrictions 
first.


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