Hi. At Thu, 25 Jul 2019 19:38:08 +0200, Jehan-Guillaume de Rorthais <j...@dalibo.com> wrote in <20190725193808.1648ddc8@firost> > On Wed, 24 Jul 2019 14:33:27 +0200 > Jehan-Guillaume de Rorthais <j...@dalibo.com> wrote: > > > On Wed, 24 Jul 2019 09:49:05 +0900 > > Michael Paquier <mich...@paquier.xyz> wrote: > > > > > On Tue, Jul 23, 2019 at 06:05:18PM +0200, Jehan-Guillaume de Rorthais > > > wrote: > [...] > > > I think that there are arguments for being more flexible with it, and > > > perhaps have a system-level view to be able to look at some of its > > > fields. > > > > Great idea. I'll give it a try to keep the discussion on. > > After some thinking, I did not find enough data to expose to justify the > creation a system-level view. As I just need the current timeline I > wrote "pg_current_timeline()". Please, find the patch in attachment. > > The current behavior is quite simple: > * if the cluster is in production, return ThisTimeLineID > * else return walrcv->receivedTLI (using GetWalRcvWriteRecPtr) > > This is really naive implementation. We should probably add some code around > the startup process to gather and share general recovery stats. This would > allow to fetch eg. the current recovery method, latest xlog file name restored > from archives or streaming, its timeline, etc. > > Any thoughts?
If replay is delayed behind timeline switch point, replay-LSN and receive/write/flush LSNs are on different timelines. When replica have not reached the new timeline to which alredy received file belongs, the fucntion returns wrong file name, specifically a name consisting of the latest segment number and the older timeline where the segment doesn't belong to. We have an LSN reporting function each for several objectives. pg_current_wal_lsn pg_current_wal_insert_lsn pg_current_wal_flush_lsn pg_last_wal_receive_lsn pg_last_wal_replay_lsn But, I'm not sure just adding further pg_last_*_timeline() to this list is a good thing.. The function returns NULL for NULL input (STRICT behavior) but returns (NULL, NULL) for undefined timeline. I don't think the differene is meaningful. regards. -- Kyotaro Horiguchi NTT Open Source Software Center
