I have occasionally been struck by extremely bad performance when it comes to the OCL Collect operator.

After debugging, I concluded that the expression used was wrong compared to my intended usage and need.

Consider this expression:

Sequence{0..7000}->collect(a| vCollectionDetails.add(Detail.Create))

My intention is to create 7000 Detail-objects and put them in the variable vCollectionDetails that has type Collection(Detail).

But this expression is extremely slow.

The main reason for the slowness is that Collect actually builds a result of all the results of the inner expression. In our case, this is a List of Lists; List of 1 detail, List of 2 details, List of 3 details...List of 6990 details etc. This is a heavy operation as 7000 thousand lists must be created and filled with 7000*7000/2 objects - I am not interested in that result. I only used the Collect operator as a convenient way to act on each.

Look at foreach for a solution or to avoid returning the list. Instead, return something simple like this:

Sequence{0..7000}->collect(a| vCollectionDetails.add(Detail.Create);0)

In this case, the collect operator returns 1 list with 7000 zeros - much faster than 24 million references to 7000 Detail objects.