I am running some crash recovery testing against 10rc1 by injecting torn page writes, using a test case which generates a lot of multixact, some naturally by doing a lot fk updates, but most artificially by calling the pg_burn_multixact function from one of the attached patches.
In 22 hours of running I got 12 instances were messages like this appear:
MultiXact member wraparound protections are disabled because oldest checkpointed MultiXact 681012168 does not exist on disk
This is not a fatal error, and no inconsistent data is found at the end of the run. But the code comments suggests that this should only happen on a server that has been upgraded from 9.3 or 9.4, which this server has not been.
Is the presence of this log message something that needs to be investigated further?
Thanks,
Jeff