[GitHub] [spark] huaxingao commented on a change in pull request #34164: [SPARK-36913][SQL] Implement createIndex and IndexExists in DS V2 JDBC (MySQL dialect)

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

huaxingao commented on a change in pull request #34164:
URL: https://github.com/apache/spark/pull/34164#discussion_r721813808



##########
File path: sql/core/src/main/scala/org/apache/spark/sql/jdbc/MySQLDialect.scala
##########
@@ -102,4 +109,59 @@ private case object MySQLDialect extends JdbcDialect {
     case FloatType => Option(JdbcType("FLOAT", java.sql.Types.FLOAT))
     case _ => JdbcUtils.getCommonJDBCType(dt)
   }
+
+  // CREATE INDEX syntax
+  // https://dev.mysql.com/doc/refman/8.0/en/create-index.html
+  override def createIndex(
+      indexName: String,
+      indexType: String,
+      tableName: String,
+      columns: Array[NamedReference],
+      columnsProperties: Array[util.Map[NamedReference, util.Properties]],
+      properties: util.Properties): String = {
+    val columnList = columns.map(col => quoteIdentifier(col.fieldNames.head))
+    var indexProperties: String = ""
+    val scalaProps = properties.asScala
+    if (!properties.isEmpty) {
+      scalaProps.foreach { case (k, v) =>
+        indexProperties = indexProperties + " " + s"$k $v"
+      }
+    }
+
+    // columnsProperties doesn't apply to MySQL so it is ignored
+    s"CREATE $indexType INDEX ${quoteIdentifier(indexName)} ON" +
+      s" ${quoteIdentifier(tableName)}" + s" (${columnList.mkString(", ")}) $indexProperties"
+  }
+
+  // SHOW INDEX syntax
+  // https://dev.mysql.com/doc/refman/8.0/en/show-index.html
+  override def indexExists(
+      conn: Connection,
+      indexName: String,
+      tableName: String,
+      options: JDBCOptions): Boolean = {
+    val sql = s"SHOW INDEXES FROM $tableName"
+    val rs = JdbcUtils.executeQuery(conn, options, sql)
+    while(rs.next()) {
+      val retrievedIndexName = rs.getString("key_name")
+      if (conf.resolver(retrievedIndexName, indexName)) {
+        return true
+      }
+    }
+    false
+  }
+
+  override def classifyException(message: String, e: Throwable): AnalysisException = {
+    if (e.isInstanceOf[SQLException]) {
+      // Error codes are from
+      // https://mariadb.com/kb/en/mariadb-error-codes/#shared-mariadbmysql-error-codes
+      e.asInstanceOf[SQLException].getErrorCode match {
+        // ER_DUP_KEYNAME
+        case 1061 =>
+          throw new IndexAlreadyExistsException(message, cause = Some(e))

Review comment:
       following the example here
   https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/jdbc/H2Dialect.scala#L30




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