[SPARK-15031][EXAMPLE] Use SparkSession in examples

## What changes were proposed in this pull request?
Use `SparkSession` according to [SPARK-15031](https://issues.apache.org/jira/browse/SPARK-15031)

`MLLLIB` is not recommended to use now, so examples in `MLLIB` are ignored in this PR.
`StreamingContext` can not be directly obtained from `SparkSession`, so example in `Streaming` are ignored too.

cc andrewor14

## How was this patch tested?
manual tests with spark-submit

Author: Zheng RuiFeng <ruifengz@foxmail.com>

Closes #13164 from zhengruifeng/use_sparksession_ii.

1 files changed, 9 insertions, 4 deletions

diff --git a/examples/src/main/python/logistic_regression.py b/examples/src/main/python/logistic_regression.py
index 7d33be7e81..01c938454b 100755
--- a/examples/src/main/python/logistic_regression.py
+++ b/examples/src/main/python/logistic_regression.py
@@ -27,7 +27,7 @@ from __future__ import print_function
 import sys
 
 import numpy as np
-from pyspark import SparkContext
+from pyspark.sql import SparkSession
 
 
 D = 10  # Number of dimensions
@@ -55,8 +55,13 @@ if __name__ == "__main__":
       Please refer to examples/src/main/python/ml/logistic_regression_with_elastic_net.py
       to see how ML's implementation is used.""", file=sys.stderr)
 
-    sc = SparkContext(appName="PythonLR")
-    points = sc.textFile(sys.argv[1]).mapPartitions(readPointBatch).cache()
+    spark = SparkSession\
+        .builder\
+        .appName("PythonLR")\
+        .getOrCreate()
+
+    points = spark.read.text(sys.argv[1]).rdd.map(lambda r: r[0])\
+        .mapPartitions(readPointBatch).cache()
     iterations = int(sys.argv[2])
 
     # Initialize w to a random value
@@ -80,4 +85,4 @@ if __name__ == "__main__":
 
     print("Final w: " + str(w))
 
-    sc.stop()
+    spark.stop()