Re: pg_upgrade < 9.3 -> >=9.3 misses a step around multixacts

Andres Freund <andres(at)2ndquadrant(dot)com> writes:
> 1) How about adding a elog(WARNING, "relation %u has invalid freeze
> limits", ...) to vac_update_datfrozenxid()? Otherwise it's a bit hard
> to understand what's going on. I wouldn't want to invest too much effort
> into the precision of the message, but some log bleat seems justified.

I considered that but wasn't really convinced it was a good idea.
You'd be getting a lot of log spam on a 9.3 installation that had
been affected by the pg_upgrade bug, until all the tables got cleaned
up (and we're intentionally not forcing that to happen quickly).

Anybody else have an opinion?

> 2) From a pedantic POV lastSane* should be initialized to
> ReadNewTransactionId()/ReadNextMultiXactId(). On a busy system we could
> otherwise consider concurrently updated values as being too new if some
> longrunning transaction finishes. Also GetOldestXmin() can sometimes go
> backwards...

If it's wrong then that's a pre-existing bug, but I don't think it's
wrong.

regards, tom lane