Getting the number of BAT accesses

Dear developers of MonetDB,

I am trying to measure the number of BAT accesses by computing per each BAT a sum of differences between highest and lowest indexes in ALGsubselect2.

I have instrumented the BAT descriptor with an additional integer value and added its initialization into BATcreate. I also added an increment operation of the value into ALGsubselect2 and modified the COLcopy function in order to carry the acquired number around.

But it all seems to be in vain, all the values remain equal to 0 when I check them via code.

Is my approach even sensible? Where else should I look to make this work?

I use MonetDB/RDF branch, the latest available version (monetdbd 1.7, monetdb 1.1).

Thank you in advance!

Best Regards, Vsevolod