Thread: Partition Rule Updating While Running?

Sorry if this is a duplicat, someone suggested posting to general as well,

I'm using PostgreSQL 8.1.4 in a Hibernate Application and I am
attempting to use partitioning via Inherited tables. At first I was
going to create a rule per sub-table based on a date range, but found
out with multiple rules postgres will only return the affected-row
count on the last rule which gives Hibernate problems. So now I'm
thinking the way to do it is just have one rule at a time and when I
want to start appending data to a new partition, just change the rule
on the parent table and also update the constraint on the last table
to reflect the date ranges contained so that constraint_exclusion will
work. this should perform better also. For instance

Starting off with:

Parent (Rule on insert instead insert into Child2)
  Child1 (Constraint date <= somedate1)
  Child2 (Constraint date > somedate1)

Now I want to create another Partition:

Create Table Child3
BEGIN
Update Parent Rule( instead insert into Child3)
somedate2 = max(date) from Child2
Update Child2 Constraint( date > somedate1 AND date <= somedate2 )
Set Constraint Child3 (date > somedate2)
END

Which ends up with:

Parent (Rule on insert instead insert into Child2)
  Child1 (Constraint date <= somedate1)
  Child2 (Constraint date > somedate1 AND date <= somedate2)
  Child3 (Constraint date > somedate2)

Anyone else tried this or expect it to work consistently (without
stopping db)? Is it possible that there could be a race condition for
the insertion and constraints or will the transaction prevent that
from occurring? I've done some testing and it seems to work but I
could just get lucky so far and not lose any data :)

Thanks for any help,
Gene

On Fri, Jul 07, 2006 at 04:39:53AM -0400, Gene wrote:
> Sorry if this is a duplicat, someone suggested posting to general as well,
>
> I'm using PostgreSQL 8.1.4 in a Hibernate Application and I am
> attempting to use partitioning via Inherited tables. At first I was
> going to create a rule per sub-table based on a date range, but found
> out with multiple rules postgres will only return the affected-row
> count on the last rule which gives Hibernate problems. So now I'm
> thinking the way to do it is just have one rule at a time and when I
> want to start appending data to a new partition, just change the rule
> on the parent table and also update the constraint on the last table
> to reflect the date ranges contained so that constraint_exclusion will
> work. this should perform better also. For instance

Why not just decide somedate2 in advance and create the constraint as a
range to start with. Then, a few days before somedate2 add a new
constraint for between somedate2 and somedate 3. Then you never have to
update any constraints...

Have a nice day,
--
Martijn van Oosterhout   <kleptog@svana.org>   http://svana.org/kleptog/
> From each according to his ability. To each according to his ability to litigate.