Robert Haas <robertmh...@gmail.com> writes: > On Mon, Sep 19, 2016 at 7:07 AM, Amit Kapila <amit.kapil...@gmail.com> wrote: >> I think you have a valid point. It seems we don't need to write WAL >> for reuse page (aka don't call _bt_log_reuse_page()), if the page is >> new, as the only purpose of that log is to handle conflict based on >> transaction id stored in special area which will be anyway zero.
> +1. This is clearly an oversight in Simon's patch fafa374f2, which introduced this code without any consideration for the possibility that the page doesn't have a valid special area. We could prevent the crash by doing nothing if PageIsNew, a la if (_bt_page_recyclable(page)) { /* * If we are generating WAL for Hot Standby then create a * WAL record that will allow us to conflict with queries * running on standby. */ - if (XLogStandbyInfoActive() && RelationNeedsWAL(rel)) + if (XLogStandbyInfoActive() && RelationNeedsWAL(rel) && + !PageIsNew(page)) { BTPageOpaque opaque = (BTPageOpaque) PageGetSpecialPointer(page); _bt_log_reuse_page(rel, blkno, opaque->btpo.xact); } /* Okay to use page. Re-initialize and return it */ but I'm not very clear on whether this is a safe fix, mainly because I don't understand what the reuse WAL record really accomplishes. Maybe we need to instead generate a reuse record with some special transaction ID indicating worst-case assumptions? regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers