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 <[email protected]> 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?
>
