huaxingao commented on a change in pull request #29324:
URL: https://github.com/apache/spark/pull/29324#discussion_r464021800
##########
File path: sql/core/src/main/scala/org/apache/spark/sql/jdbc/JdbcDialects.scala
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@@ -184,15 +189,56 @@ abstract class JdbcDialect extends Serializable {
/**
* Rename an existing table.
*
- * TODO (SPARK-32382): Override this method in the dialects that don't
support such syntax.
- *
* @param oldTable The existing table.
* @param newTable New name of the table.
* @return The SQL statement to use for renaming the table.
*/
def renameTable(oldTable: String, newTable: String): String = {
s"ALTER TABLE $oldTable RENAME TO $newTable"
}
+
+ /**
+ * Alter an existing table.
+ *
+ * @param tableName The name of the table to be altered.
+ * @param changes Changes to apply to the table.
+ * @return The SQL statement to use for altering the table.
+ */
+ def alterTable(tableName: String, changes: Seq[TableChange]): Array[String]
= {
+ val updateClause = mutable.ArrayBuilder.make[String]
+ for (change <- changes) {
+ change match {
+ case add: AddColumn =>
+ add.fieldNames match {
+ case Array(name) =>
+ val dataType = JdbcUtils.getJdbcType(add.dataType(),
this).databaseTypeDefinition
+ updateClause += s"ALTER TABLE $tableName ADD COLUMN $name
$dataType"
+ case _ =>
+ throw new IllegalArgumentException(s"Unsupported TableChange
fieldNames" +
+ s" ${add.fieldNames}")
+ }
+ case rename: RenameColumn =>
+ rename.fieldNames match {
+ case Array(name) =>
+ updateClause += s"ALTER TABLE $tableName RENAME COLUMN $name TO
${rename.newName}"
+ case _ =>
+ throw new IllegalArgumentException(s"Unsupported TableChange
fieldNames" +
+ s" ${rename.fieldNames}")
+ }
+ case delete: DeleteColumn =>
+ delete.fieldNames match {
+ case Array(name) =>
+ updateClause += s"ALTER TABLE $tableName DROP COLUMN $name"
+ case _ =>
+ throw new IllegalArgumentException(s"Unsupported TableChange
fieldNames" +
+ s" ${delete.fieldNames}")
+ }
+ case _ => throw new IllegalArgumentException(s"JDBC alterTable has
Unsupported" +
Review comment:
I added ```UpdateColumnType``` and ```UpdateColumnNullability```. I
didn't add ```UpdateColumnComment``` and ```UpdateColumnPosition```. Seems most
of the databases don't support these two, so I didn't implement these two.
I added ```UpdateColumnNullability```, but didn't add a test for it yet,
because the test failed at the check here
```
case update: UpdateColumnNullability =>
val field = findField("update", update.fieldNames)
val fieldName = update.fieldNames.quoted
if (!update.nullable && field.nullable) {
alter.failAnalysis(
s"Cannot change nullable column to non-nullable:
$fieldName")
}
```
I am confused. I thought the whole point of ```UpdateColumnNullability``` is
to change nullable column to non-nullable?
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