Bruce Momjian <pgman@candle.pha.pa.us> writes:
>> If it's not too much of a bother, what do they mean?
> OK, when one backend changes a system table, it invalidates the system
> caches used by other backends. I don't remember the exact messages, but
> they deals with cache invalidation overflows that are properly handled
> by each backend and do not present any cause for concern.
What they really mean is that some backend has failed to keep up with
the stream of cache invalidation messages being issued by some other
backend. The system recovers from this by simply invalidating *all*
cache entries when it happens. The reason there's a message is
(1) a version or three back, there were various bugs that might be
triggered by these events. AFAIK they're all fixed.
(2) if you see this a *lot* (not just occasionally) it might suggest
that the cache inval message buffer size ought to be increased. So
someone once felt there was value in notifying the user.
regards, tom lane