Add migration doc and update R doc

R/pkg/R/DataFrame.R

@@ -1886,7 +1886,7 @@ setMethod("except",
 #' @param df A SparkSQL DataFrame
 #' @param path A name for the table
 #' @param source A name for external data source
-#' @param mode One of 'append', 'overwrite', 'error', 'ignore' save mode
+#' @param mode One of 'append', 'overwrite', 'error', 'ignore' save mode (it is 'error' by default)
 #'
 #' @family DataFrame functions
 #' @rdname write.df
@@ -1951,7 +1951,7 @@ setMethod("saveDF",
 #' @param df A SparkSQL DataFrame
 #' @param tableName A name for the table
 #' @param source A name for external data source
-#' @param mode One of 'append', 'overwrite', 'error', 'ignore' save mode
+#' @param mode One of 'append', 'overwrite', 'error', 'ignore' save mode (it is 'error' by default)
 #'
 #' @family DataFrame functions
 #' @rdname saveAsTable

docs/sparkr.md

@@ -387,3 +387,10 @@ The following functions are masked by the SparkR package:
 Since part of SparkR is modeled on the `dplyr` package, certain functions in SparkR share the same names with those in `dplyr`. Depending on the load order of the two packages, some functions from the package loaded first are masked by those in the package loaded after. In such case, prefix such calls with the package name, for instance, `SparkR::cume_dist(x)` or `dplyr::cume_dist(x)`.
 
 You can inspect the search path in R with [`search()`](https://stat.ethz.ch/R-manual/R-devel/library/base/html/search.html)
+
+
+# Migration Guide
+
+## Upgrading From SparkR 1.6 to 1.7
+
+ - Before Spark 1.7, the default save mode is `append` in api saveDF/write.df/saveAsTable, it is changed to `error` to be consistent with scala api.