I see we recommend using the age(xid) function to check for XID
wraparound:
http://www.postgresql.org/docs/8.3/static/routine-vacuuming.html#VACUUM-FOR-WRAPAROUND
However, the function only does a subtraction with no adjustment for
overflow, and considering it returns a signed int, it can't even display
the full range of valid values:
test=> \df age List of functions Schema | Name | Result data type |
Argument data
types------------+------+------------------+----------------------------------------------------------...pg_catalog |
age | integer | xid
For example:
test=> select txid_current(); txid_current-------------- 397(1 row)test=> select age('10000'::xid);
age--------9602(1 row)
Seems this is a bug. I think the fix is to do the arithmetic in int8
and return an int8.
-- Bruce Momjian <bruce@momjian.us> http://momjian.us EnterpriseDB
http://enterprisedb.com
+ If your life is a hard drive, Christ can be your backup. +