> I took at a first crack at coding up an implementation of
> relation_is_distinct_for() tonight.
I am not sure if this will help or not, but on the 8.4 code base we
implemented two functions:
- getCandidateKeys() - would recursively traverse a tree from a given
node to the leaf nodes and determine the candidate keys for the
intermediate relation produced by that node
- getJoinCard() - determined the join cardinality of a hash join node
(1:1, 1:N, etc.) based on the candidate keys of the two input relations
It worked pretty well for our tests with equi-joins, but I am sure it is
missing many cases. I have attached the code which we used
(cardinalityFuncs.c). Some of the helper functions may also be useful
(convertUniqueIndexesToCandidateKeys, getJoinAttrs).
--
Ramon Lawrence