Group functions by Spark SQL category

Signed-off-by: Xiaoguang Sun <[email protected]>

sql/core/src/main/scala/org/apache/spark/sql/jdbc/MySQLDialect.scala

@@ -49,42 +49,42 @@ private case class MySQLDialect() extends JdbcDialect with SQLConfHelper with No
   // See https://dev.mysql.com/doc/refman/8.4/en/built-in-function-reference.html
   // The functions listed here have the same signature and similar semantics,
   // and can be supported with existing mechanism.
-  private val supportedSQLFunctions = Set(
+  private val supportedConditionalFunctions = Set ("COALESCE")
+  private val supportedDateAndTimestampFunctions = Set("DATE_ADD", "DATE_DIFF")
+  private val supportedEncryptionFunctions = Set("SHA1", "SHA2", "MD5")
+  private val supportedMathmaticalFunctions = Set (
     "ABS",
-    "COALESCE",
+    "ACOS",
+    "ASIN",
+    "ATAN",
+    "ATAN2",
+    "COS",
+    "COT",
+    "CRC32",
+    "DEGREES",
+    "EXP",
     "GREATEST",
     "LEAST",
-    "RAND",
+    "LN",
     "LOG10",
     "LOG2",
-    "LN",
-    "EXP",
     "POWER",
-    "SQRT",
-    "SIN",
-    "COS",
-    "TAN",
-    "COT",
-    "ASIN",
-    "ACOS",
-    "ATAN",
-    "ATAN2",
-    "DEGREES",
     "RADIANS",
+    "RAND",
     "SIGN",
-    "SUBSTRING",
-    "UPPER",
-    "LOWER",
-    "SHA1",
-    "SHA2",
-    "MD5",
-    "CRC32",
-    "BIT_LENGTH",
-    "CHAR_LENGTH",
-    "CONCAT")
+    "SQRT",
+    "SIN",
+    "TAN")
+  private val supportedStringFunctions =
+    Set("BIT_LENGTH", "CHAR_LENGTH", "CONCAT", "LOWER", "SUBSTRING", "UPPER")
 
   private val supportedFunctions =
-    supportedAggregateFunctions ++ Set("DATE_ADD", "DATE_DIFF") ++ supportedSQLFunctions
+    supportedAggregateFunctions ++
+      supportedConditionalFunctions ++
+      supportedDateAndTimestampFunctions ++
+      supportedEncryptionFunctions ++
+      supportedMathmaticalFunctions ++
+      supportedStringFunctions
 
   override def isSupportedFunction(funcName: String): Boolean =
     supportedFunctions.contains(funcName)