Re: Question Regarding Locks

Just so that I am not getting this wrong:

> BTW, a handy proxy for "row has not changed" is to see if its XMIN
> system column is still the same as before.
Considering that my business objects remember XMIN from when
they first got the row would the following sequence make sure
I am in good shape ?

begin;
select ... for update;
update ... set ... where
my_pk=<my_pk_value>
AND
xmin=<the_old_xmin>

This should either update 1 row in which case I can commit or
zero rows in which case I need to rollback and handle the merge
conflict. The reasoning would be that the condition
my_pk=my_pk_value would select the row I am interested in
while xmin=the_old_xmin would ensure that row hasn't been
modified.

Am I right or is there a flaw in my thinking ?

Thanks,
Karsten
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