[SPARK-8437] [DOCS] Using directory path without wildcard for filename slow for large number of files with wholeTextFiles and binaryFiles

Note that 'dir/*' can be more efficient in some Hadoop FS implementations that 'dir/'

Author: Sean Owen <sowen@cloudera.com>

Closes #7036 from srowen/SPARK-8437 and squashes the following commits:

0e813ae [Sean Owen] Note that 'dir/*' can be more efficient in some Hadoop FS implementations that 'dir/'

(cherry picked from commit 5d30eae56051c563a8427f330b09ef66db0a0d21)
Signed-off-by: Andrew Or <andrew@databricks.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/core/src/main/scala/org/apache/spark/SparkContext.scala b/core/src/main/scala/org/apache/spark/SparkContext.scala
index b4c0d4c2f5..f8af710de7 100644
--- a/core/src/main/scala/org/apache/spark/SparkContext.scala
+++ b/core/src/main/scala/org/apache/spark/SparkContext.scala
@@ -824,6 +824,8 @@ class SparkContext(config: SparkConf) extends Logging with ExecutorAllocationCli
    * }}}
    *
    * @note Small files are preferred, large file is also allowable, but may cause bad performance.
+   * @note On some filesystems, `.../path/*` can be a more efficient way to read all files in a directory
+   *       rather than `.../path/` or `.../path`
    *
    * @param minPartitions A suggestion value of the minimal splitting number for input data.
    */
@@ -871,9 +873,11 @@ class SparkContext(config: SparkConf) extends Logging with ExecutorAllocationCli
    *   (a-hdfs-path/part-nnnnn, its content)
    * }}}
    *
-   * @param minPartitions A suggestion value of the minimal splitting number for input data.
-   *
    * @note Small files are preferred; very large files may cause bad performance.
+   * @note On some filesystems, `.../path/*` can be a more efficient way to read all files in a directory
+   *       rather than `.../path/` or `.../path`
+   *
+   * @param minPartitions A suggestion value of the minimal splitting number for input data.
    */
   @Experimental
   def binaryFiles(