The map "toCarry" will return you (partitionIndex, None) for empty partition.
So I think line 51 won't fail. Line 58 can fail if "lastNotNullRow" is None. You of course should check if an Option has value or not before you access it. As the "toCarry" returned is the following when I tested your codes: Map(1 -> Some(FooBar(Some(2016-01-04),lastAssumingSameDate)), 0 -> Some(FooBar(Some(2016-01-02),second))) As you seen, there is no None, so the codes work without failure. But of course it depends how your data partitions. For empty partition, when you do mapPartitions, it just gives you an empty iterator as input. You can do what you need. You already return a None when you find an empty iterator in preparing "toCarry". So I was wondering what you want to ask in the previous reply. geoHeil wrote > Thanks a lot, Holden. > > @Liang-Chi Hsieh did you try to run > https://gist.github.com/geoHeil/6a23d18ccec085d486165089f9f430f2 for me > that is crashing in either line 51 or 58. Holden described the problem > pretty well. Ist it clear for you now? > > Cheers, > Georg > > Holden Karau [via Apache Spark Developers List] < > ml-node+s1001551n20516h45@.nabble >> schrieb am Mo., 9. Jan. 2017 um > 06:40 Uhr: > >> Hi Georg, >> >> Thanks for the question along with the code (as well as posting to stack >> overflow). In general if a question is well suited for stackoverflow its >> probably better suited to the user@ list instead of the dev@ list so I've >> cc'd the user@ list for you. >> >> As far as handling empty partitions when working mapPartitions (and >> similar), the general approach is to return an empty iterator of the >> correct type when you have an empty input iterator. >> >> It looks like your code is doing this, however it seems like you likely >> have a bug in your application logic (namely it assumes that if a >> partition >> has a record missing a value it will either have had a previous row in >> the >> same partition which is good OR that the previous partition is not empty >> and has a good row - which need not necessarily be the case). You've >> partially fixed this problem by going through and for each partition >> collecting the last previous good value, and then if you don't have a >> good >> value at the start of a partition look up the value in the collected >> array. >> >> However, if this also happens at the same time the previous partition is >> empty, you will need to go and lookup the previous previous partition >> value >> until you find the one you are looking for. (Note this assumes that the >> first record in your dataset is valid, if it isn't your code will still >> fail). >> >> Your solution is really close to working but just has some minor >> assumptions which don't always necessarily hold. >> >> Cheers, >> >> Holden :) >> On Sun, Jan 8, 2017 at 8:30 PM, Liang-Chi Hsieh <[hidden email] >> <http:///user/SendEmail.jtp?type=node&node=20516&i=0>> >> wrote: >> >> >> Hi Georg, >> >> Can you describe your question more clear? >> >> Actually, the example codes you posted in stackoverflow doesn't crash as >> you >> said in the post. >> >> >> geoHeil wrote >> > I am working on building a custom ML pipeline-model / estimator to >> impute >> > missing values, e.g. I want to fill with last good known value. >> > Using a window function is slow / will put the data into a single >> > partition. >> > I built some sample code to use the RDD API however, it some None / >> null >> > problems with empty partitions. >> > >> > How should this be implemented properly to handle such empty >> partitions? >> > >> http://stackoverflow.com/questions/41474175/spark-mappartitionswithindex-handling-empty-partitions >> > >> > Kind regards, >> > Georg >> >> >> >> >> >> ----- >> >> >> Liang-Chi Hsieh | @viirya >> Spark Technology Center >> http://www.spark.tc/ >> >> -- >> View this message in context: >> http://apache-spark-developers-list.1001551.n3.nabble.com/handling-of-empty-partitions-tp20496p20515.html >> >> Sent from the Apache Spark Developers List mailing list archive at >> Nabble.com. >> >> --------------------------------------------------------------------- >> >> To unsubscribe e-mail: [hidden email] >> <http:///user/SendEmail.jtp?type=node&node=20516&i=1> >> >> >> >> >> -- >> Cell : 425-233-8271 <(425)%20233-8271> >> Twitter: https://twitter.com/holdenkarau >> If you reply to this email, your message will be added to the discussion >> below: >> >> http://apache-spark-developers-list.1001551.n3.nabble.com/handling-of-empty-partitions-tp20496p20516.html >> To unsubscribe from handling of empty partitions, click here >> <http://apache-spark-developers-list.1001551.n3.nabble.com/template/NamlServlet.jtp?macro=unsubscribe_by_code&node=20496&code=Z2Vvcmcua2YuaGVpbGVyQGdtYWlsLmNvbXwyMDQ5NnwtMTgzMzc4NTU4MQ==> >> . >> NAML >> <http://apache-spark-developers-list.1001551.n3.nabble.com/template/NamlServlet.jtp?macro=macro_viewer&id=instant_html%21nabble%3Aemail.naml&base=nabble.naml.namespaces.BasicNamespace-nabble.view.web.template.NabbleNamespace-nabble.view.web.template.NodeNamespace&breadcrumbs=notify_subscribers%21nabble%3Aemail.naml-instant_emails%21nabble%3Aemail.naml-send_instant_email%21nabble%3Aemail.naml> >> ----- Liang-Chi Hsieh | @viirya Spark Technology Center http://www.spark.tc/ -- View this message in context: http://apache-spark-developers-list.1001551.n3.nabble.com/handling-of-empty-partitions-tp20496p20519.html Sent from the Apache Spark Developers List mailing list archive at Nabble.com. --------------------------------------------------------------------- To unsubscribe e-mail: dev-unsubscr...@spark.apache.org
