Thanks Andreas. That was a quick response.
So way 1 must be quicker.
am 10.03.2006, um 10:46:39 -0500 mailte Emi Lu folgendes:
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.
Because of MVCC every UPDATE is practical a DELETE + INSERT.
Way1: you have only one DELETE+INSERT, Way2 one hundred, and you have
100 dead rows until the next VACUUM.
HTH, Andreas
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