Github user dongjoon-hyun commented on a diff in the pull request:
https://github.com/apache/spark/pull/14086#discussion_r71470476
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/DataFrameWriter.scala ---
@@ -419,8 +422,13 @@ final class DataFrameWriter[T] private[sql](ds:
Dataset[T]) {
}
if (mode == SaveMode.Overwrite && tableExists) {
- JdbcUtils.dropTable(conn, table)
- tableExists = false
+ if (extraOptions.getOrElse("truncate", "false").toBoolean &&
+ JdbcUtils.isCascadingTruncateTable(url) == Some(false)) {
+ JdbcUtils.truncateTable(conn, table)
--- End diff --
First of all, it will raise exceptions if one of the column names are
different.
For the different column type with same column name, it will work like
`SaveMode.Append` operation.
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