Tom Lane escribió: > Alvaro Herrera <alvhe...@2ndquadrant.com> writes: > > Here's the final version. I think this is ready to go in. > > I got around to reviewing this today. I'm pretty seriously annoyed at > the definition of dlist_delete: it should *not* require the list header. > The present coding simply throws away one of the primary advantages of > a doubly-linked list over a singly-linked list, namely that you don't > have to have your hands on the list header in order to unlink a node. > This isn't merely academic either, as I see that the patch to catcache > code actually added a field to struct catctup to support making the > list header available. That's a complete waste of 8 bytes (on a 64-bit > machine) per catalog cache entry. The only thing it buys for us is > the ability to run dlist_check, which is something that isn't even > compiled (not even in an Assert build), and which doesn't actually do > that much useful even if it is compiled --- for instance, there's no way > to verify that the nodes were actually in the list claimed.
Oops. I mentioned this explicitely somewhere in the discussion. I assumed you had seen that, and that you would have complained had you found it objectionable. (It's hard enough to figure out if people don't respond because they don't have a problem with something, or just because they didn't see it.) On the other hand, it's convenient to remove them, because in predicate.c there are plenty of SHM_QUEUE node removals which is clearly easier to port over to dlist if we don't have to figure out exactly which list each node is in. (Maybe in other SHM_QUEUE users as well, but that's the most complex of the bunch.) > I think we should remove the head argument at least from dlist_delete, > and probably also dlist_insert_after and dlist_insert_before. There are more functions that get the list head just to run the check. Can I assume that you don't propose removing the argument from those? (dlist_next_node, dlist_prev_node I think are the only ones). -- Álvaro Herrera http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
