Github user felixcheung commented on a diff in the pull request:
https://github.com/apache/spark/pull/22455#discussion_r219030350
--- Diff: docs/sparkr.md ---
@@ -450,6 +450,42 @@ print(model.summaries)
{% endhighlight %}
</div>
+### Eager execution
+
+If the eager execution is enabled, the data will be returned to R client
immediately when the `SparkDataFrame` is created. Eager execution can be
enabled by setting the configuration property
`spark.sql.repl.eagerEval.enabled` to `true` when the `SparkSession` is started
up.
+
+<div data-lang="r" markdown="1">
+{% highlight r %}
+
+# Start up spark session with eager execution enabled
+sparkR.session(master = "local[*]", sparkConfig =
list(spark.sql.repl.eagerEval.enabled = "true"))
+
+df <- createDataFrame(faithful)
+
+# Instead of displaying the SparkDataFrame class, displays the data
returned
+df
+
+##+---------+-------+
+##|eruptions|waiting|
+##+---------+-------+
+##| 3.6| 79.0|
+##| 1.8| 54.0|
+##| 3.333| 74.0|
+##| 2.283| 62.0|
+##| 4.533| 85.0|
+##| 2.883| 55.0|
+##| 4.7| 88.0|
+##| 3.6| 85.0|
+##| 1.95| 51.0|
+##| 4.35| 85.0|
+##+---------+-------+
+##only showing top 10 rows
+
+{% endhighlight %}
+</div>
+
+Note that the `SparkSession` created by `sparkR` shell does not have eager
execution enabled. You can stop the current session and start up a new session
like above to enable.
--- End diff --
actually I think the suggestion should be to set that in the `sparkR`
command line as spark conf?
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