*Holders are for both input and output. You can also use CompleWriter for output and FieldReader for input if you want to write or read a complex value.
I don't think we've provided a really clean way to construct a Repeated*Holder for output purposes. You can probably do it by reaching into a bunch of internal interfaces in Drill. However, I would recommend using the ComplexWriter output pattern for now. This will be a little less efficient but substantially less brittle. I suggest you open up a jira for using a Repeated*Holder as an output. On Sat, Jul 4, 2015 at 1:38 PM, Ted Dunning <ted.dunn...@gmail.com> wrote: > Holders are for input, I think. > > Try the different kinds of writers. > > > > On Sat, Jul 4, 2015 at 12:49 PM, Jim Bates <jba...@maprtech.com> wrote: > > > Using a repeatedholder as a @param I've got working. I was working on a > > custom aggregator function using DrillAggFunc. In this I can do simple > > things but If I want to build a list values and do something with it in > the > > final output method I think I need to use RepeatedHolders in the > > @Workspace. To do that I need to create a new one in the setup method. I > > can't get one built. They all require a BufferAllocator to be passed in > to > > build it. I have not found a way to get an allocator yet. Any > suggestions? > > > > On Sat, Jul 4, 2015 at 1:37 PM, Ted Dunning <ted.dunn...@gmail.com> > wrote: > > > > > If you look at the zip function in > > > https://github.com/mapr-demos/simple-drill-functions you can have an > > > example of building a structure. > > > > > > The basic idea is that your output is denoted as > > > > > > @Output > > > BaseWriter.ComplexWriter writer; > > > > > > The pattern for building a list of lists of integers is like this: > > > > > > writer.setValueCount(n); > > > ... > > > BaseWriter.ListWriter outer = writer.rootAsList(); > > > outer.start(); // [ outer list > > > ... > > > // for each inner list > > > BaseWriter.ListWriter inner = outer.list(); > > > inner.start(); > > > // for each inner list element > > > inner.integer().writeInt(accessor.get(i)); > > > } > > > inner.end(); // ] inner list > > > } > > > outer.end(); // ] outer list > > > > > > > > > > > > On Sat, Jul 4, 2015 at 10:29 AM, Jim Bates <jba...@maprtech.com> > wrote: > > > > > > > I have working aggregation and simple UDFs. I've been trying to > > document > > > > and understand each of the options available in a Drill UDF. > > > Understanding > > > > the different FunctionScope's, the ones that are allowed, the ones > that > > > are > > > > not. The impact of different cost categories. The different steps > > needed > > > > to understand handling any of the supported data types and > structures > > in > > > > drill. > > > > > > > > Here are a few of my current road blocks. Any pointers would be > greatly > > > > appreciated. > > > > > > > > > > > > 1. I've been trying to understand how to correctly use > > RepeatedHolders > > > > of whatever type. For this discussion lets start with a > > > > RepeatedBigIntHolder. I'm trying to figure out the best way to > > create > > > a > > > > new > > > > one. I have not figured out where in the existing drill code > someone > > > > does > > > > this. If I use a RepeatedBigIntHolder as a Workspace object is is > > > null > > > > to > > > > start with. I created a new one in the startup section of the udf > > but > > > > the > > > > vector was null. I can find no reference in creating a new > > > BigIntVector. > > > > There is a way to create a BigIntVector and I did find an example > of > > > > creating a new VarCharVector but I can't do that using the drill > jar > > > > files > > > > from 1.0. The org.apache.drill.common.types.TypeProtos and > > > > the org.apache.drill.common.types.TypeProtos.MinorType classes do > > not > > > > appear to be accessible from the drill jar files. > > > > 2. What is the best way to close out a UDF in the event it > generates > > > an > > > > exception? Are there specific steps one should follow to make a > > clean > > > > exit > > > > in a catch block that are beneficial to Drill? > > > > > > > > > >
