I wonder if anyone can explain to me just HOW Data Services will decide to pushdown a certain function to the database. I thought I knew but I'm now not so sure. I thought that it was ALL specified through the AL_FUNCINFO table but I now believe that not to be the case as I have been looking into the Date_Diff function which seems to work without issue in SQLAnywhere yet not in SAP IQ. It was at this point that the mystery seemed to take a turn for the worse as upon investigating the AL_FUNCINFO table in my repository as to why this might be the case there seems to only 1 record for the date_diff function which is for the engine itself and referfences a 'db_func' field called date_diff (not surprisingly).
Yet... If I use a date_diff expression against SQL Anywhere it knows to use the DateDiff function in the sql for pushdown
How on earth is it making this assumption given that there is no record within the data-table? Is there another table I should be looking at too?