I have at occasions been struck by extremely bad performance when it comes to the ocl Collect operator.

After debugging I have 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 very (extremly) slow.

The main reason for the slowliness is that collect actually build 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. And this is a heavy operation as 7000 thousand lists must be created and filled with 7000*7000/2 objects - and I am not even 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 - and 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 - very much faster than 24 million references to 7000 Detail objects.