On Wed, Dec 13, 2017 at 4:20 PM, Thomas Munro <thomas.mu...@enterprisedb.com> wrote: > On Wed, Dec 13, 2017 at 3:41 PM, Amit Kapila <amit.kapil...@gmail.com> wrote: >> Good. I hope that the patch I have posted above is able to resolve >> this problem. I am asking as you haven't explicitly mentioned that. > > I can confirm that your patch fixes the problem for forward scans. > That is, I can see it reaching the BTP_DELETED case via an extra LOG > statement I added, and it worked correctly. Good. > > I don't know how to make it hit the backwards scan case. I can get a > backward scan in a worker by changing the query to "select count(*) > from (select * from jobs where id + 1 > id order by status desc) ss" > but I suspect that _bt_walk_left() may be hiding deleted pages from us > so the condition may not be reachable with this technique.
Hmm, no that's not right: clearly it can return half-dead or deleted pages to the caller. So I don't know why I never seem to encounter any, despite concurrent vacuums producing them; maybe something to do with the interlocking you get with vacuum when you traverse the btree by walking left -- my btree-fu is not yet strong enough. -- Thomas Munro http://www.enterprisedb.com
