beliefer commented on code in PR #49453:
URL: https://github.com/apache/spark/pull/49453#discussion_r1971150984


##########
connector/docker-integration-tests/src/test/scala/org/apache/spark/sql/jdbc/v2/MySQLIntegrationSuite.scala:
##########
@@ -241,6 +241,84 @@ class MySQLIntegrationSuite extends 
DockerJDBCIntegrationV2Suite with V2JDBCTest
     assert(rows10(0).getString(0) === "amy")
     assert(rows10(1).getString(0) === "alex")
   }
+
+  // MySQL Connector/J uses collation 'utf8mb4_0900_ai_ci' as collation for 
connection.
+  // The MySQL server 9.1.0 uses collation 'utf8mb4_0900_ai_ci' for database 
by default.
+  // This method uses string colume directly as the result of cast has the 
same collation.
+  def testCastStringTarget(stringLiteral: String, stringCol: String): String = 
stringCol
+
+  test("SPARK-50793: MySQL JDBC Connector failed to cast some types") {
+    val tableName = catalogName + ".test_cast_function"
+    withTable(tableName) {
+      val stringValue = "0"
+      val stringLiteral = "'0'"
+      val stringCol = "string_col"
+      val longValue = 0L
+      val longCol = "long_col"
+      val binaryValue = Array[Byte](0x30)
+      val binaryLiteral = "x'30'"
+      val binaryCol = "binary_col"
+      val doubleValue = 0.0
+      val doubleLiteral = "0.0"
+      val doubleCol = "double_col"
+      // CREATE table to use types defined in Spark SQL
+      sql(
+        s"CREATE TABLE $tableName ($stringCol STRING, $longCol LONG, " +
+          s"$binaryCol BINARY, $doubleCol DOUBLE)")
+      sql(
+        s"INSERT INTO $tableName VALUES($stringLiteral, $longValue, 
$binaryLiteral, $doubleValue)")
+
+      def testCast(
+          castType: String,
+          sourceCol: String,
+          targetCol: String,
+          targetDataType: DataType,
+          targetValue: Any): Unit = {
+        val sql = s"SELECT CAST($sourceCol AS $castType) AS target " +
+          s"FROM $tableName WHERE CAST($sourceCol AS $castType) = $targetCol"
+        val df = spark.sql(sql)

Review Comment:
   I think we should create the test table with the MySQL DDL syntax. For 
example,
   ```
   CREATE TABLE t
   (
       c1 VARCHAR(20) CHARACTER SET utf8mb4,
       c2 TEXT CHARACTER SET latin1 COLLATE latin1_general_cs
   );
   ```
   And then let `MySQLDialect.getCatalystType` supports convert JDBC collation 
to Spark collation and `MySQLDialect.getJDBCType` supports convert Spark 
collation to JDBC collation.
   At last we test with
   `select * from t where c2 = 'abc'` in Spark. In fact, we will push down the 
query
    `select * from t where c2 = latin1'abc' COLLATE latin1_general_cs` to MySQL.



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