Errors in logs

I'm getting these errors in my logs. they don't seem bad but I like to be
sure:

010708.02:33:03.966  [2369] SIInsertDataEntry: table is 70% full, signaling postmaster
010708.02:33:03.966 [27400] pmdie 12
010708.02:33:03.991 [27400] SignalChildren: sending signal 12 to process 2369
010708.02:33:03.991 [27400] SignalChildren: sending signal 12 to process 24757
010708.02:33:03.991 [27400] SignalChildren: sending signal 12 to process 9657
010708.02:33:04.420  [9657] NOTICE:  InvalidateSharedInvalid: cache state reset
010708.04:00:03.924  [2535] NOTICE:  RegisterSharedInvalid: SI buffer overflow
010708.04:00:03.924  [2535] NOTICE:  InvalidateSharedInvalid: cache state reset
010710.04:09:26.357 [18323] NOTICE:  RegisterSharedInvalid: SI buffer overflow
010710.04:09:26.357 [18323] NOTICE:  InvalidateSharedInvalid: cache state reset
010711.02:45:25.467 [25307] SIInsertDataEntry: table is 70% full, signaling post master
010711.02:45:25.467 [27400] pmdie 12
010711.02:45:25.523 [27400] SignalChildren: sending signal 12 to process 25307
010711.02:45:25.523 [27400] SignalChildren: sending signal 12 to process 22906
010711.02:45:25.523 [27400] SignalChildren: sending signal 12 to process 24757
010711.04:03:48.358 [25494] NOTICE:  RegisterSharedInvalid: SI buffer overflow
010711.04:03:48.358 [25494] NOTICE:  InvalidateSharedInvalid: cache state reset

Seems to usually happen during vacuums. Should I be worried?
--
Martijn van Oosterhout <kleptog@svana.org>
http://svana.org/kleptog/
> It would be nice if someone came up with a certification system that
> actually separated those who can barely regurgitate what they crammed over
> the last few weeks from those who command secret ninja networking powers.