I don't think my experiment is suprising, it's my fault:
To move away from my case, I wrote a test program, which generates data
randomly, and cast the key to string:
import randomimport operator
COUNT = 23333COUNT_PARTITIONS = 36LEN = 233
rdd = sc.parallelize(((str(random.randint(1, LEN)), 1) for i in xrange(COUNT)),
COUNT_PARTITIONS)reduced =
rdd.reduceByKey(operator.add).sortByKey()print(reduced.count(), LEN) # the
result is valid if count == LEN
More about my environment: I'm running Spark on a small Mesos cluster, I'm
always using pyspark shell with Python 2.7.9, IPython 3.0.0. The operating
system is ArchLinux.
And, there is a node, running x86 Arch Linux, while the others x86_64.
The problem arises, as long as the x86 node and x64 nodes works together.
Nothing wrong if there is only a x86 node in the cluster, or just x64 nodes.
And currently only reduceByKey with int32 keys makes sense.
Maybe I should update my system.
Date: Sat, 18 Apr 2015 08:28:50 -0700
Subject: Re: Does reduceByKey only work properly for numeric keys?
From: yuzhih...@gmail.com
To: lovejay-lovemu...@outlook.com
CC: user@spark.apache.org
Can you show us the function you passed to reduceByKey() ?
What release of Spark are you using ?
Cheers
On Sat, Apr 18, 2015 at 8:17 AM, SecondDatke <lovejay-lovemu...@outlook.com>
wrote:
I'm trying to solve a Word-Count like problem, the difference lies in that, I
need the count of a specific word among a specific timespan in a social message
stream.
My data is in the format of (time, message), and I transformed (flatMap etc.)
it into a series of (time, word_id), the time is represented with Python
datetime.datetime class. And I continued to transform it to ((time, word_id),
1) then use reduceByKey for result.
But the dataset returned is a little weird, just like the following:
format:((timespan with datetime.datetime, wordid), freq)
((datetime.datetime(2009, 10, 6, 2, 0), 0), 8)((datetime.datetime(2009, 10, 6,
3, 0), 0), 3)((datetime.datetime(2009, 10, 6, 3, 0), 0), 14)
As you can see, there are DUPLICATED keys, but as a result of reducedByKey, all
keys SHOULD BE UNIQUE.
I tried to convert the key to a string (like '2006-12-02 21:00:00-000') and
reducedByKey again, the problem stays. It seems the only way left for me is
convert the date to a timestamp, but this time it works.
Is this expected behavior of reduceByKey(and all other transformations that
work with keys)?
Currently I'm still working on it.
