On Sat, Aug 12, 2023 at 11:50:36AM +0530, Amit Kapila wrote: > > We will need that complexity somewhere, > > so why not in pg_upgrade? > > > > I don't think we need the complexity of version-specific checks if we > do what we do in get_control_data(). Basically, invoke > version-specific pg_replslotdata to get version-specific slot > information. There has been a proposal for a tool like that [1]. Do > you have something better in mind? If so, can you please explain the > same a bit more?
Yes, if you want to break it out into a separate tool and then have pg_upgrade call/parse it like it calls/parses pg_controldata, that seems fine. > > > > After reading the control file and the slots' state files we > > > > check if slot's confirmed_flush_lsn matches the latest checkpoint LSN > > > > in the control file (BTW maybe we can get slot name and plugin name > > > > here instead of using pg_dump?). > > > > > > But isn't the advantage of doing via pg_dump (in binary_mode) that we > > > allow some outside core in-place upgrade tool to also use it if > > > required? If we don't think that would be required then we can > > > probably use the info we retrieve it in pg_upgrade. > > > > You mean the code reading the slot file? I don't see the point of > > adding user complexity to enable some hypothetical external usage. > > It is not just that we need a slot reading facility but rather mimic > something like pg_get_replication_slots() where we have to know the > walstate (WALAVAIL_REMOVED, etc.) as well. I am not against it but am > not sure that we do it for any other object in the upgrade. Can you > please point me out if we have any such prior usage? Even if we don't > do it today, we can start doing now if that makes sense but it appears > to me that we are accessing contents of data-dir/WAL by invoking some > other utilities like pg_controldata, pg_resetwal, so something similar > would make sense here. Actually, what we do here also somewhat depends > on what we decide for the other point we are discussing above in the > email. Yes, if there is value in having that information available via the command-line tool, it makes sense to add it. Let me add that developers have complained how pg_upgrade scrapes the output pg_controldata rather than reading the file, and we are basically do that some more with this. However, I think that is an appropriate approach. -- Bruce Momjian <br...@momjian.us> https://momjian.us EDB https://enterprisedb.com Only you can decide what is important to you.
