OO and tuples of different types

Came across this comment in execTuples.c...
*In the implementation of nested-dot queries such as*"retrieve (EMP.hobbies.all)", a single scan may return tuples*of
manytypes, so now we return pointers to tuple descriptors*along with tuples returned via the tuple table.  This
means*wenow have a bunch of routines to diddle the slot descriptors*too.  -cim 1/18/90
 

Hmm. Another few years of reading the source and I'll probably
understand all this :-) :-(.

Can anybody provide any insight? Like What EMP.hobbies.all meant in
postquel?

-- 
Chris Bitmead
mailto:chris@bitmead.com