Combining two rowsets in ADLA without join on clause - azure-data-lake

Question

I've got two types of input files I'm loading into an ADLA job. In one, I've got a bunch of data (left) and in another, I've got a list of values that are important to me (right).
As an example here, let's say I'm using the following in my "left" rowset:
| ID | URL |
|----|-------------------------|
| 1 | https://www.google.com/ |
| 2 | https://www.yahoo.com/ |
| 3 | https://www.hotmail.com/|
I'll have something like the following in my right rowset:
| ID | Name | Regex | Exceptions | Other Lookup Val |
|----|-------|-------------|------------|------------------|
| 1 | ThisA | /[a-z]{3,}/ | abc | 091238 |
| 2 | ThatA | /[a-z]{3,}/ | xyz | lksdf9 |
| 3 | OtherA| /[a-z]{3,}/ | def | 098143 |
As each are loaded via an EXTRACT statement, both are in separate rowsets. Ideally, I'd like to be able to load all the values for both rowsets and loop through the right one to run a series of calculations against the left one to find a match per various business rules. Notably, there's no value to simply join on, nor is it a simple Regex evaluation, but rather something a bit more involved. Thus, the output might just look something like the "left" rowset:
| ID | URL |
|----|-------------------------|
| 1 | https://www.google.com/ |
| 3 | https://www.hotmail.com/|
Now, a COMBINER is the only UDO I see that accepts two rowsets, but the U-SQL syntax requires that I do some sort of join statement here. There's no common identifier between each of the rowsets though, so there's nothing to join on, which suddenly makes this seem less ideal. Of the attribute options defined at https://learn.microsoft.com/en-us/azure/data-lake-analytics/data-lake-analytics-u-sql-programmability-guide#use-user-defined-combiners, I'd like to specify this as a Full because I'd need each of the left values available to evaluate against each of the right ones, but again, no shared identifier to do this on.
I then tried to use a REDUCER that accepted an IRowset in the IReducer constructor as a parameter, then tried to just pass the rowset in from the U-SQL, but it didn't like that syntax.
Is there any way to perform this custom combining in a manner that doesn't require a JOIN ON clause?

Answer 1

It sounds like you may be able to use an IProcessor. This would allow you to analyze each row in the RIGHT set and add a column (with a value based on your business rules) that you can subsequently use to join to the LEFT set.
[Adding a bit more detail]: You could also do this twice, once for the left and once for the right to create an artificial join column, like row_number or some such.