The implementation of concat has only two arguments and its fixed. We
rewrite the concat function in DrillOptiq
<https://github.com/apache/incubator-drill/blob/master/exec/java-exec/src/main/java/org/apache/drill/exec/planner/logical/DrillOptiq.java#L357>
class to be stacked on top of each other so that it uses only two arguments.
Eg: concat('a', 'b', 'c') ==> concat(concat('a', 'b'), 'c')
Thanks
Mehant
On 9/12/14, 10:50 AM, Matt Burgess wrote:
Thanks all for the great info, I will look into the Complex type stuff.
I'm still confused about concatenation though, it seems that concat is defined
having two parameters but I can call it on more than that (I tried up to 5).
How does that work, is it generated by Freemarker or something to support
different (but discrete) numbers of params?
Thanks again,
Matt
On Sep 12, 2014, at 1:33 PM, Jinfeng Ni <[email protected]> wrote:
VarArgs is currently not supported. To add support of VarArgs, things
might require to be changed:
1. In function template, a new annotation would be added to mark parameter
as VarArgs.
2. In FunctionConverter, need recognize this new annotation, and build the
function holder accordingly.
3. FunctionResolver need add logic to handle VarArgs during function
resolution.
4. The run-time code generation for VarArgs also would require change.
You may check with Yash, since he might have more thoughts about VarArgs
support.
If you want to have a function which takes an array or map, you may want to
consider using complex type's FieldReader / ComplexWriter interface, just
like Ted suggested. (Take a look at JsonConvertTo /JsonConvertFrom as
example).
On Fri, Sep 12, 2014 at 8:15 AM, Ted Dunning <[email protected]> wrote:
On Fri, Sep 12, 2014 at 6:31 AM, Matt Burgess <[email protected]> wrote:
SELECT transform("concatTab", *) from dfs.`my_file.csv`
the intent here is that a result set is returned that basically changes a
CSV file to a TSV result set.
This should be done at a higher level than the SQL itself.
