On Thu, Dec 21, 2023 at 3:10 PM Andres Freund <and...@anarazel.de> wrote: > > Hi, > > On 2023-12-21 09:21:04 +0900, Michael Paquier wrote: > > While listening at Bertrand's talk about logical decoding on standbys > > last week at Prague, I got surprised by the fact that we do not > > reflect in the catalogs the reason why a conflict happened for a slot. > > There are three of them depending on ReplicationSlotInvalidationCause: > > - WAL removed. > > - Invalid horizon. > > - Insufficient WAL level. > > It should be extremely rare to hit any of these other than "WAL removed", so > I'm not sure it's worth adding interface complexity to show them. > > > > ReplicationSlotCtl holds this information, so couldn't it be useful > > for monitoring purposes to know why a slot got invalidated and add a > > column to pg_get_replication_slots()? This could just be an extra > > text conflicting_reason, defaulting to NULL when there's nothing to > > see. > > Extra columns aren't free from a usability perspective. IFF we do something, I > think it should be a single column with a cause.
Thanks for the feedback. But do you mean that we replace existing 'conflicting' column with 'cause' in both the function and view (pg_get_replication_slots() and pg_replication_slots)? Or do you mean that we expose 'cause' from pg_get_replication_slots() and use that to display 'conflicting' in pg_replication_slots view? And if we plan to return/display cause from either function or view, then shall it be enum 'ReplicationSlotInvalidationCause' or description/text corresponding to enum? In the other feature being discussed "Synchronize slots from primary to standby" [1] , there is a requirement to replicate invalidation cause of slot from the primary to standby and thus it is needed in enum form there. And thus there was a suggestion earlier to have the function return enum-value and let the view display it as text/description to the user. So kindly let us know your thoughts. [1] - https://www.postgresql.org/message-id/514f6f2f-6833-4539-39f1-96cd1e011...@enterprisedb.com thanks Shveta