> On Mar 19, 2020, at 4:13 PM, pabloa98 <pablo...@gmail.com> wrote:
>
>
>
> On Thu, Mar 19, 2020 at 2:50 PM Rob Sargent <robjsarg...@gmail.com
> <mailto:robjsarg...@gmail.com>> wrote:
>
>
> > On Mar 19, 2020, at 3:36 PM, pabloa98 <pablo...@gmail.com
> > <mailto:pablo...@gmail.com>> wrote:
> >
> > Hello,
> >
> > My schema requires a counter for each combination of 2 values. Something
> > like:
> >
> > CREATE TABLE counter(
> > group INT NOT NULL,
> > element INT NOT NULL,
> > seq_number INT NOT NULL default 0,
> > CONSTRAINT PRIMARY KEY (group, element)
> > );
> >
> > For each entry in counter, aka for each (group, element) pair, the model
> > requires a seq_number.
> >
> > If I use a table "counter", I could still have counter collisions between 2
> > transactions. I need truly sequence behavior. Is that possible by using a
> > table like "counter" table, where the counter could be increased out of the
> > transaction so it performs as a sequence without having race conditions
> > between concurrent transactions?
> >
> > The other option is to create sequences for each new pair of (group,
> > element) using triggers. There are millions of pairs. So this approach will
> > generate millions of sequences.
> >
> > How a PostgreSQL database would behave having millions of sequences in a
> > schema? Would it degrade its performance? Is there any negative impact?
> >
> > Regards
> >
> > Pablo
> >
>
> To clarify, are you hoping for consecutive numbers as the each row is added
> to the table, i.e. “serial”?
>
> What is the intension of “seq_number”?
> >
> >
>
>
> the idea is to have like a serial sequence, but for each pair of (group,
> element).
>
> so that when we insert rows in another table, we could have something like:
>
>
> group, element, event_id, ...
> 1, 1, 1
> 1, 1, 2
> 1, 1, 3
> 2, 1, 1
> 1, 1, 4
> 1, 3, 1
> 1, 1, 5
> 1, 3, 2
> 2, 1, 2
> 2, 1, 3
>
> The 3rd column is the sequence number we get from the appropriate sequence
> created by the trigger.
>
> I want to implement a variation of https://stackoverflow.com/a/30204854
> <https://stackoverflow.com/a/30204854> and that will generate millions of
> sequences.
>
>
Then I don’t thing group/element can be a PRIMARY KEY
