[GitHub] spark pull request #14086: [SPARK-16463][SQL] Support `truncate` option in O...

[gatorsmile <gi...@git.apache.org>]

Github user gatorsmile commented on a diff in the pull request:

    https://github.com/apache/spark/pull/14086#discussion_r71468419
  
    --- 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 --
    
    If `truncateTable` failed due to a non fatal exception, should we fall back to the previous way (i.e., drop and create)? This is a design decision. CC @srowen @rxin 


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