I have added another idea for index-only scans to the TODO list:
> A third idea would be for a heap scan to check if all rows are visible
> and if so set a per-table flag which can be checked by index scans.
> Any change to the table would have to clear the flag. To detect
> changes during the heap scan a counter could be set at the start and
> checked at the end --- if it is the same, the table has not been
> modified --- any table change would increment the counter.
-- Bruce Momjian <bruce@momjian.us> http://momjian.us EnterpriseDB
http://www.enterprisedb.com
+ If your life is a hard drive, Christ can be your backup. +