sunxiaoguang commented on code in PR #49453:
URL: https://github.com/apache/spark/pull/49453#discussion_r1919505376
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sql/core/src/main/scala/org/apache/spark/sql/jdbc/MySQLDialect.scala:
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@@ -112,6 +112,21 @@ 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 SMALLINT,
INTEGER and BIGINT.
+ // To avoid breaking code relying on ResultSet metadata, we support
BIGINT only at
+ // this time.
+ case LongType => "SIGNED INTEGER"
+ // MySQL uses BINARY in the cast function for the type BLOB
+ case BinaryType => "BINARY"
+ case _ =>
getJDBCType(dataType).map(_.databaseTypeDefinition).getOrElse(dataType.typeName)
Review Comment:
Yes, they are valid statements. The problem comes from different set of
target type identifiers. The original type is less important, for example we
can do this for string type as well:
```sql
SELECT cast('123' AS SIGNED INTEGER)
```
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