Merge Join Output Bug?

I've run into something that looks like a bug to me but I wanted to run it by the board:

Merge join 2 sorted tables.

Table1: ColumnA : Sort Order 1, ColumnB Sort Order 2

Table2 : ColumnA: Sort Order 1, ColumnB Sort Order 2, ColumnC not sorted

Merge Join the two tables on ColumnA and ColumnB...

Choose the following as output columns

A + B + C = works

C = works

A + C = works

B + C = NOT work.. error message: The column with the SortKeyPosition value of 0 is not valid. It should be 2.

Basically if you choose one or more of the sorted columns in the output at least one of them has to be the column with Sort position 1 or you'll get that error.

Is this a bug or intentional? If you do not have sort column 1 in the output that output could no longer be considered sorted... so perhaps the error is related to that (instead of error I'd expect some warning about the sorting). Interesting that it lets you choose C only becuase that also makes the output unsorted.

I see your point Chris.

I think it is intential -

. The reason why B+C not work is because column B has a non-zero sortKeyPosition which indicates the output (to which B belongs) should be sorted (in other words, the output's "isSorted" property is true), but the output can not find a column with SortKeyPosition 1

. As for why C column only works is because the output is then not sorted.

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Thanks

wenyang