Peter Eisentraut wrote:
> So in order to correctly answer the question, is the sequence about to
> run out, you need to look not only at
> the sequence but also any columns it is associated with. check_postgres
> figures this out, but it's complicated and slow, and not easy to do
> manually.
It strikes me that this is a compelling argument for setting a sensible
MAXVALUE when creating a sequence for a SERIAL, rather than binding
the sequence to a datatype.
In existing releases the SERIAL code sets the maxvalue to 2^63 even
though it knows that the column is limited to 2^31.
It looks like setting it to 2^31 would be enough for the sake of
monitoring.
More generally, what is of interest for the monitoring is how close
the sequence's last_value is from its max_value, independently of an
underlying type.
2^{15,31,63} are specific cases of particular interest, but there's
no reason to only check for these limits when you can do it
for every possible limit.
For instance if a user has a business need to limit an ID to 1 billion,
they should alter the sequence to a MAXVALUE of 1 billion, and be
interested in how close they are from that, not from 2^31.
Best regards,
--
Daniel Vérité
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Twitter: @DanielVerite
