[GitHub] [spark] teeyog commented on a change in pull request #25287: [SPARK-28552][SQL]Identification of different dialects insensitive to case by JDBC URL prefix

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teeyog commented on a change in pull request #25287: [SPARK-28552][SQL]Identification of different dialects insensitive to case by JDBC URL prefix
URL: https://github.com/apache/spark/pull/25287#discussion_r339867433
 
 

 ##########
 File path: sql/core/src/main/scala/org/apache/spark/sql/jdbc/JdbcDialects.scala
 ##########
 @@ -56,13 +57,26 @@ case class JdbcType(databaseTypeDefinition : String, jdbcNullType : Int)
  */
 @DeveloperApi
 abstract class JdbcDialect extends Serializable {
+  /**
+   * The tag of the database, it must be lowercase, the subsequent will match
+   * the corresponding dialect through this tag, so it must be strictly one-to-one
+   * correspondence with jdbc url,such as:
+   * mysql  url:  jdbc:mysql://localhost/db  dbTag: mysql
+   * oracle url:  jdbc:oracle://localhost/db dbTag: oracle
+   * db2    url:  jdbc:db2://localhost/db    dbTag: db2
+   * ......
+   */
+  def dbTag: String
 
 Review comment:
   So how do you look like this, the canHandle in each implementation is cover to lowercase
   ```
   private case object MySQLDialect extends JdbcDialect {
   
     override def canHandle(url : String): Boolean =
         url.toLowerCase(Locale.ROOT).startsWith("jdbc:mysql")
   ```

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