Hi Alex, We have a slide to hlep you understand how to build cube.I don't know whether you have read this? This will hlep you understand derived and hierarchy.
http://www.slideshare.net/YangLi43/design-cube-in-apache-kylin for your case about hierarchy,log_date should not be included in hierarchy ,here's a bug you help find it.we will follow this. also .more document and UI enhancement will be done to help user build cube easily. Thanks!! On Fri, Jun 12, 2015 at 5:07 PM, alex schufo <[email protected]> wrote: > I am trying to create a simple cube with a fact table and 3 dimensions. > > I have read the different slideshares and wiki pages, but I found that the > documentation is not very specific on how to manage hierarchies. > > Let's take this simple example : > > Fact table: productID, storeID, logDate, numbOfSell, etc. > > Date lookup table : logDate, week, month, quarter, etc. > > I specified Left join on logDate, actually when I specify this I find it > not very clear which one is considered to be the Left table and which one > is considered to be the Right table. I assumed the Fact table was the left > table and the Lookup table the right table, looking at it now I think that > might be a mistake (I am just interested in dates for which there are > results in the fact table). > > If I use the auto generator it creates a derived dimension, I don't think > that's what I need. > > So I created a hierarchy, but again to me it's clearly indicated if I > should create ["quarter", "month", "week", "log_date"] or ["logDate", > "week", "month", "quarter"]? > > Also should I include log_date in the hierarchy? To me it was more > intuitive not to include it because it's already the join, but it created > the cube without it and I cannot query by date, it says that "log_date" is > not found in the date table (it is in the Hive table but not the cube > built). If I include it in the hierarchy the cube build fails with this > error : > > java.lang.NullPointerException: Column DEFAULT.DATE_TABLE.LOG_DATE > does not exist in row key desc > at > org.apache.kylin.cube.model.RowKeyDesc.getColDesc(RowKeyDesc.java:158) > at > org.apache.kylin.cube.model.RowKeyDesc.getDictionary(RowKeyDesc.java:152) > at > org.apache.kylin.cube.model.RowKeyDesc.isUseDictionary(RowKeyDesc.java:163) > at > org.apache.kylin.cube.cli.DictionaryGeneratorCLI.processSegment(DictionaryGeneratorCLI.java:51) > at > org.apache.kylin.cube.cli.DictionaryGeneratorCLI.processSegment(DictionaryGeneratorCLI.java:42) > at > org.apache.kylin.job.hadoop.dict.CreateDictionaryJob.run(CreateDictionaryJob.java:53) > at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:70) > at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:84) > at > org.apache.kylin.job.common.HadoopShellExecutable.doWork(HadoopShellExecutable.java:63) > at > org.apache.kylin.job.execution.AbstractExecutable.execute(AbstractExecutable.java:107) > at > org.apache.kylin.job.execution.DefaultChainedExecutable.doWork(DefaultChainedExecutable.java:50) > at > org.apache.kylin.job.execution.AbstractExecutable.execute(AbstractExecutable.java:107) > at > org.apache.kylin.job.impl.threadpool.DefaultScheduler$JobRunner.run(DefaultScheduler.java:132) > at > java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) > at > java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) > at java.lang.Thread.run(Thread.java:744) > > result code:2 > > > I think it might be useful to improve the documentation to explain this > more clearly and not just the basic steps because building a cube even on > short time ranges takes some time so learning by trial / error is very time > consuming. > > Same thing for the derived dimensions, should I include ["storeID", > "storeName"] or just ["storeName"]? The second option seems to work for me. > > Thanks >
