On 2013-06-27 11:16:25 +0530, Amit Kapila wrote: > On Wednesday, June 26, 2013 10:19 PM Fujii Masao wrote: > > On Wed, Jun 26, 2013 at 8:57 PM, Amit Kapila <amit.kap...@huawei.com> > > >> > One more use case for which this utility was done is as below: > > >> > It will be used to decide that on new-standby (old-master) > > whether > > >> a full > > >> > backup is needed from > > >> > New-master(old-standby). > > >> > The backup is required when the data page in old-master precedes > > >> > the last applied LSN in old-standby (i.e., new-master) at the > > >> moment > > >> > of the failover. > > >> > > >> That's exactly what I was afraid of. Unless I miss something the > > tool > > >> is > > >> *NOT* sufficient to do this. > > > > > > You mean to say if user knows the max LSN of data pages in old-master > > and > > > last applied LSN in new master, he cannot decide whether > > > Full backup is needed? It should be straightforward decision that > > skip a > > > backup if that old-master LSN is less than the new-master (i.e., last > > > applied LSN, IOW, timeline switch LSN). > > > It was proposed as a usecase in this below mail: > > > http://www.postgresql.org/message-id/CAHGQGwHyd1fY0hF0qKh0-uKDh- > > gcbYxMOFBYVk > > > kh4jzji-f...@mail.gmail.com > > > > I guess he meant the commit hint bit problem. > > True, after reading the thread mentioned by Andres, I got the reason he was > pointing why it is not sufficient. > So can it be useful if database has checksums enabled?
I think for that usecase its far more useful to work on getting pg_rewind since that has a chance of working when local WAL has been applied that hadn't yet shipped to the other side (which is frequently the case). Greetings, Andres Freund -- Andres Freund 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
