Re: Could not open file pg_multixact/offsets/ ERROR on 9.3.4 - Mailing list pgsql-hackers

Aha, so the problem looks like this:

- all multixact contents was purged (9.2 to 9.3 incompatibility)

- the only offset was the 0000 file created by initidb during bootstrap

- truncation code in vacuum assumed the page related to multixact it tried to truncate actually exists

- the assumption was based on the fact that there exists a page earlier than the one it tried to truncate

- due to the wrong assumption, there was an attempt to truncate a non-existing page, resulting in the error.

Now that makes sense, thank you very much. Vacuum runs w/o issues once I removed that 0000 file.

I think it should be safe to recommend removing the 0000 file for everyone with the same problem.

The 2 cases where 0000 file is actually used are:

- when the are no more then 2 pages of offsets (0000 and 0001) since the server creation

- when the multixacts wrapped around and 0000 is not the first page.

I think in both cases  there will be no gaps in segments in offsets,

so the problem won't be there in the first place.

Cheers,