shiguangsheng(at)huawei(dot)com writes:
> PostgreSQL version: 8.3.17
8.3 is long out of support (and 8.3.17 even more so).
> I added a function that is used to scan the specified table.
You didn't show us enough of that function to be sure, but I rather
suspect that you're failing to pay attention to the
XMIN/XMAX COMMITTED/INVALID status bits. Once those are set it is
no longer appropriate to try to fetch the actual commit status,
because the system is allowed to truncate away the relevant part of
pg_clog.
regards, tom lane