Github user danielvdende commented on a diff in the pull request:
https://github.com/apache/spark/pull/19911#discussion_r155622687
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/jdbc/DB2Dialect.scala ---
@@ -48,5 +48,7 @@ private object DB2Dialect extends JdbcDialect {
case _ => None
}
- override def isCascadingTruncateTable(): Option[Boolean] = Some(false)
+ override def getTruncateQuery(table: String): String = {
+ s"TRUNCATE $table"
--- End diff --
The `JdbcDialect` object now no longer provides a default implementation
for `getTruncateQuery` (as per @dongjoon-hyun 's suggestion). The reason is
that this explicitly forces dialects to implement a truncate operation without
side effects.
One thing I don't like about this solution is the code duplication across
dialects. But it does prevent dialects from inheriting default behaviour and
(accidentally) truncating with side effects.
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