selectivity calculation for or_clause is wrong ?

Hi all,

I have a question about the calculation of selectivity.

I see the following code in set_rest_selec() in clausesel.c.

cost_clause = clausenode->selectivity;

/*
* Check to see if the selectivity of this clause or any
'or'
* subclauses (if any) haven't been set yet.
*/
if (cost_clause <= 0 || valid_or_clause(clausenode))
{

Why is valid_or_clause(clausenode) necessary ?

This means that even if selectivity is set,set_rest_selec()
calls compute_clause_selec() if the target clause is a
valid_or_clause.
compute_clause_selec() would add the selectivity of
elements of or_clause to the current selectivity.

AFAIC,compute_clause_selec() is called twice at least
( from add_restrict_and_join_to_rel() in initsplan.c
and set_rest_selec() in clausesel.c)
and seems to accumulate the result by repetition if
the target clause is a valid_or_clause.

Regards.

Hiroshi Inoue
Inoue(at)tpf(dot)co(dot)jp