Eng 6553 group by alias

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It is bad form to change a for loop counter in the middle of the loop.
If you are sure that the list contains duplicates, then you should change the for loop to "...; i+=2) {"
You should also assert that unresolvedExpressions.get(i) == unresolvedExpressions.get(i+1).
Also, if before the loop you assert that size is an even number "assert((size / 2) * 2 == size);" you don't need the size+1 < limit check.