WAL

Hi,

if I do something like this:

BEGIN;
UPDATE tbl SET data='something' WHERE pkey='selector';
UPDATE tbl SET data=NULL WHERE pkey='selector';
COMMIT;

Given 'selector' actually exists, I get a separate WAL entry for each of
the updates. My question is, does the first update actually hit the data
file?

If I am only interested in the first update hitting the WAL, does it make
sense to do something like the above in a transaction? Would that help to
keep the table small in a high concurrency situation? The table itself has
a small fillfactor. So, in most cases there should be enough space to do a
HOT update. For that HOT update, is that second update setting data to NULL
beneficial or rather adverse?

Thanks,
Torsten