Thanks for answering, it was a good guess, I really didn't mark it, but unfortunately it didn't solve my problem. It still falls down, when I try to access the argument. But it seems strange to me, that converting to Relation is OK: Relation index_rel = (Relation) PG_GETARG_POINTER(1); and also that comparing to NULL is OK: if (index_rel == NULL). Obviously the problem comes, when touching inside the structure in RelationGetNumberOfBlocks. I'm running it on Windows XP, but i guess that should be no problem in this case? Don't you have possibly any other ideas? I'm implementing a framework for indexing into PG as my diploma work, so it's quite importatnt to me... Thanks, David Hoksza ________________________________ 19. března 2006, 22:43:48, napsal jste: TL> david.hoksza@xxxxxxxxx writes: >> Hi, I'm trying to implement my own access method. Now I've implemented >> and compiled it but I've problems when I try to use it. TL> Wild guess: did you mark all your functions as V1 call convention? TL> The internal functions don't need to be marked, but dynamically loaded TL> ones do. TL> regards, tom lane