Hi:
In join_is_legal(), i wonder wether the 2 "return false" statements can be
covered by any query.
/*
* If one input contains min_lefthand and the other contains
* min_righthand, then we can perform the SJ at this join.
*
* Reject if we get matches to more than one SJ; that implies we're
* considering something that's not really valid.
*/
if (bms_is_subset(sjinfo->min_lefthand, rel1->relids) &&
bms_is_subset(sjinfo->min_righthand, rel2->relids))
{
if (match_sjinfo)
return false; /* invalid join path */
match_sjinfo = sjinfo;
reversed = false;
}
else if (bms_is_subset(sjinfo->min_lefthand, rel2->relids) &&
bms_is_subset(sjinfo->min_righthand, rel1->relids))
{
if (match_sjinfo)
return false; /* invalid join path */
match_sjinfo = sjinfo;
reversed = true;
}
There is no query in regression test suite that can render the 2 decisions
based on match_sjinfo true, nor can i figure out such a query. Can these
conditions ever be true? If they can be true, what is the query that make them
true?
Any feedback is welcome.
