sunxiaoguang commented on code in PR #49453:
URL: https://github.com/apache/spark/pull/49453#discussion_r1912725632
##########
sql/core/src/main/scala/org/apache/spark/sql/jdbc/MySQLDialect.scala:
##########
@@ -112,6 +112,19 @@ private case class MySQLDialect() extends JdbcDialect with
SQLConfHelper with No
} else {
super.visitAggregateFunction(funcName, isDistinct, inputs)
}
+
+ override def visitCast(expr: String, exprDataType: DataType, dataType:
DataType): String = {
+ val databaseTypeDefinition = dataType match {
+ // MySQL uses CHAR in the cast function for the type LONGTEXT
+ case StringType => "CHAR"
+ // MySQL uses SIGNED INTEGER in the cast function for the types
SMALLINT, INTEGER and BIGINT
+ case ShortType | IntegerType | LongType => "SIGNED INTEGER"
Review Comment:
You are right, MySQL doesn't support casting to Short and Integer. But
luckily, the wire protocol and JDBC driver implementation works with the same
BIGINT result for Short, Integer and Long types.
```java
import java.sql.*;
public class JDBC {
public static void main(String[] args) throws Exception {
String host = "localhost";
int port = 3306;
String username = "root";
String password = "";
String database = "test";
try (Connection conn = DriverManager.getConnection(
String.format("jdbc:mysql://%s:%d/%s", host, port, database),
username, password);
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery("SELECT CAST(1 AS SIGNED
INTEGER)")) {
if (rs.next()) {
System.out.println("Short: " + rs.getShort(1));
System.out.println("Integer: " + rs.getInt(1));
System.out.println("Long: " + rs.getLong(1));
}
}
}
}
```
And here is the output
```bash
java -cp mysql-connector-java-8.0.25.jar JDBC.java
Short: 1
Integer: 1
Long: 1
```
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