sunxiaoguang commented on code in PR #49453:
URL: https://github.com/apache/spark/pull/49453#discussion_r1914266781
##########
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:
Data types are validated as well in the test to make sure in the case MySQL
only cast to BIGINT, we always get the right types expecting from Spark side.
```scala
......
val shortValue = 0.toShort
val integerValue = 0
val longValue = 0L
......
def testCast(castType: String, sourceCol: String, targetCol: String,
sourceValue: Any, targetValue: Any): Unit = {
val sql =
s"""SELECT $sourceCol, CAST($sourceCol AS $castType) FROM
$tableName
|WHERE CAST($sourceCol AS $castType) = $targetCol""".stripMargin
val rows = spark.sql(sql).collect()
assert(rows.length === 1, s"Failed to cast $sourceCol to $castType")
val row = rows(0)
assert(row.get(0) === sourceValue, s"$sourceCol does not equal to
$sourceValue")
assert(row.get(0).getClass == sourceValue.getClass,
s"$sourceCol has different type from $sourceValue")
assert(row.get(1) === targetValue,
s"CAST($sourceCol AS $castType) does not equal to $targetValue")
assert(row.get(1).getClass == targetValue.getClass,
s"CAST($sourceCol AS $castType) has different type from
$targetValue")
}
......
testCast("SHORT", "string_col", "short_col", stringValue, shortValue)
testCast("INTEGER", "string_col", "integer_col", stringValue,
integerValue)
testCast("LONG", "string_col", "long_col", stringValue, longValue)
```
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