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Diffstat (limited to 'python/pyspark/rdd.py')
| -rw-r--r-- | python/pyspark/rdd.py | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/python/pyspark/rdd.py b/python/pyspark/rdd.py index 4f74824ba4..07578b8d93 100644 --- a/python/pyspark/rdd.py +++ b/python/pyspark/rdd.py @@ -1152,6 +1152,10 @@ class RDD(object): Group the values for each key in the RDD into a single sequence. Hash-partitions the resulting RDD with into numPartitions partitions. + Note: If you are grouping in order to perform an aggregation (such as a + sum or average) over each key, using reduceByKey will provide much better + performance. + >>> x = sc.parallelize([("a", 1), ("b", 1), ("a", 1)]) >>> map((lambda (x,y): (x, list(y))), sorted(x.groupByKey().collect())) [('a', [1, 1]), ('b', [1])] |