Re: add_partial_path() may remove dominated path but still in use

Kohei KaiGai <kaigai(at)heterodb(dot)com> writes:
> I've investigated a crash report of PG-Strom for a few days, then I doubt
> add_partial_path() can unexpectedly release dominated old partial path
> but still referenced by other Gather node, and it leads unexpected system
> crash.

Hm. This seems comparable to the special case in plain add_path, where it
doesn't attempt to free IndexPaths because of the risk that they're still
referenced. So maybe we should just drop the pfree here.

However, first I'd like to know why this situation is arising in the first
place. To have the situation you're describing, we'd have to have
attempted to make some Gather paths before we have all the partial paths
for the relation they're for. Why is that a good thing to do? It seems
like such Gathers are necessarily being made with incomplete information,
and we'd be better off to fix things so that none are made till later.

regards, tom lane