[GENERAL] WAL

if I do something like this:

BEGIN;

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