I would assume that the driver has to count the number of lines in the json file anyway. Otherwise, how could it tell the workers which lines they should work on?
2016-05-31 10:03 GMT+02:00 Gavin Yue <yue.yuany...@gmail.com>: > If not reading the whole dataset, how do you know the total number of > records? If not knowing total number, how do you choose 30%? > > > > > On May 31, 2016, at 00:45, pbaier <patrick.ba...@zalando.de> wrote: > > > > Hi all, > > > > I have to following use case: > > I have around 10k of jsons that I want to use for learning. > > The jsons are all stored in one file. > > > > For learning a ML model, however, I only need around 30% of the jsons > (the > > rest is not needed at all). > > So, my idea was to load all data into a RDD and then use the rdd.sample > > method to get my fraction of the data. > > I implemented this, and in the end it took as long as loading the whole > data > > set. > > So I was wondering if Spark is still loading the whole dataset from disk > and > > does the filtering afterwards? > > If this is the case, why does Spark not push down the filtering and load > > only a fraction of data from the disk? > > > > Cheers, > > > > Patrick > > > > > > > > > > -- > > View this message in context: > http://apache-spark-user-list.1001560.n3.nabble.com/Behaviour-of-RDD-sampling-tp27052.html > > Sent from the Apache Spark User List mailing list archive at Nabble.com. > > > > --------------------------------------------------------------------- > > To unsubscribe, e-mail: user-unsubscr...@spark.apache.org > > For additional commands, e-mail: user-h...@spark.apache.org > > > -- Patrick Baier Payment Analytics *E-Mail: patrick.ba...@zalando.de <patrick.ba...@zalando.de>*
