>>You may find message #689364 useful.
>
>It seems to me that I solved the problem by setting order to nothing and restoring it afterward. BTW, would your solution work in case of filter set on a table?

That is the part of this as well, it's just that my approach initially uses the index to find the scope (in records) of current key value, so that it doesn't scan entire table when scanning it with order of 0.

It should - it employs scan for, and calc while, which are both filter sensitive.