> P(A|B) = P(A and B) / P(B). Well, until this point we've discussed failure cases involving 'AND' conditions. What about 'OR' conditions? I think the current optimizer computes the selectivity as 's1+s2 - s1*s2' (at least that's what I found in backend/optimizer/path/clausesel.c:630).
Sometimes that may return nearly 2x the actual selectivity, but in general it's a reasonable estimate. Are there any severe failure cases that produce much worse estimates? regards Tomas -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
