About updates

[Emi Lu <emilu@xxxxxxxxxxxxxxxxx>]

Hello,

postgresql 8.0.1, in a plpgsql function

To update columns' values in a table (without OID), if I ran:
1. "update table1 set col1 = ..., col2 = ... ... col100 ="

or
2.
"update table1 set col1 = "
...
"update table1 set col100 = "

way 1 only has one disk I/O, right? While way 2 is more time consuming 
since there is disk I/O when a update is ran.

Thanks a lot,
Ying