does update table with identical values actually write to disk?

From: Clay Colburn <>
Date: Mon, 1 Nov 2010 10:57:02 -0700
Message-ID: <>

I can't seem to find any documentation on this, probably because the search terms are so generic. Basically I'm wondering if you execute an update statement where you are setting the same value that already exists on disk, does the optimizer know that they are the same and forgo the write to disk, or does it just blindly write the same value over top of the old record and move on?

So for example if I have a row of data:

create table my_test(id number, val varchar(10)); insert into my_test(1, 'one');

and I run the statement

update my_test set val = 'one' where id = 1;

will it write the new value to disk or evaluate that it is the same and skip the write?


Received on Mon Nov 01 2010 - 12:57:02 CDT

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