[GitHub] [spark] huaxingao commented on a change in pull request #30142: [SPARK-33095] Follow up, support alter table column rename.

[GitBox <gi...@apache.org>]

huaxingao commented on a change in pull request #30142:
URL: https://github.com/apache/spark/pull/30142#discussion_r513616044



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File path: sql/core/src/main/scala/org/apache/spark/sql/jdbc/MySQLDialect.scala
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@@ -57,6 +58,25 @@ private case object MySQLDialect extends JdbcDialect {
     s"ALTER TABLE $tableName MODIFY COLUMN ${quoteIdentifier(columnName)} $newDataType"
   }
 
+  // See Old Syntax: https://dev.mysql.com/doc/refman/5.6/en/alter-table.html
+  // According to https://dev.mysql.com/worklog/task/?id=10761 old syntax works for
+  // both versions of MySQL i.e. 5.x and 8.0
+  // The old syntax requires us to have type definition. Since we do not have type
+  // information, we throw the exception.
+  override def getRenameColumnQuery(
+      tableName: String,
+      columnName: String,
+      newName: String): String = {
+    if (SQLConf.get.jdbcMySQLVersion.matches("^8\\.[0-9].*")) {

Review comment:
       Instead of using a session config, we probably want to get database version using `DatabaseMetaData` in `JdbcUtils.altertable` and pass the info here, and only do `RENAME` if version >= 8
   ```
   conn.getMetaData.getDatabaseMajorVersion
   ```




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