Web Designer - Collection Performance (v8.0)

Hi Experts

I am seeing some strange behaviour in terms of front end performance

I have 2 collections (accprodonLoad, accprodonClick), both containing AccProducts loaded from the database

First collection (accprodOnLoad) contains 20,000 objects, other one (accprodOnClick) contains 1500 objects. The first collection has a boolean property IsSelected which I want to set to TRUE if the object also exists in the second collection. For this, I put a simple update collection node with the following filter

uid_Accproduct in (select uid_Accproduct from accprodonClick)

This does work, but it takes over 3 minutes to update the collection. There are no event handlers or anything else running off the back of it. To reproduce, I ran the following query and the query also takes a long time (around 2 minutes) to run

select * from accprodonLoad where uid_Accproduct in( select uid_Accproduct from accprodonClick)

This should be a relatively quick lookup however it is taking a very very long time - any ideas? Any other ways to update the accprodOnLoad collection (I have even tried Foreach but that is also slow)

Thanks

kin