Question on partman extension while relation exist

Hi Yudhi,

I think disabling foreign keys before maintenance will help.

Regards,
Muhammad Ikram
Bitnine global

On Tue, Jul 2, 2024 at 11:41 AM yudhi s <learnerdatabase99@gmail.com> wrote:

Hello All,
In postgres we are seeing issues during automatic partition maintenance
using pg_partman extension. So basically it automatically creates one new
partition and drops one historical partition each day based on the set
retention period in part_config. We just call it like
partman.run_maintenance_proc('table_name');

While there exists foreign key relationships between the partitioned
tables, Mainly during dropping the parent partitions it takes a lot of
time, as it validates every child table partitions record and also is
taking lock longer. Ideally it should check only the respective parent
partition, but it's not doing that because the foreign key is defined in
table level rather than partition level. So we are planning to create the
foreign keys on the partition level but not at table level.

And we were thinking of doing it dynamically by having an "event trigger"
which will fire on "create statement" i.e while the "create new partition"
statement will be triggered by the Pg_partman. It will try to also create
the foreign key constraints on the new child partition referring to the
respective parent partition during the same time. So that things will be
automated.

But now we are stuck in one scenario , say for example if we execute the
pg_partman for the parent table first then it will create the new partition
independently which is fine, but when it will try to drop the historical
partition, it will complain stating the child partition already exists.

On the other hand,

If we run the pg_partman for the child table first, then it will drop the
historical child partition without any issue , however it will throw an
error while creating the foreign key , as because the respective parent
partition has not yet been created.

Need advice, how we should handle this scenario. Basically in which order
we should call the "pg_partman.run_maintenance_proc" for the parent and
child tables?

--
Muhammad Ikram

On Tue, 2 Jul, 2024, 12:43 pm Muhammad Ikram, <mmikram@gmail.com> wrote:

Hi Yudhi,

I think disabling foreign keys before maintenance will help.

--
Muhammad Ikram

Do you mean to say call the parent table first for maintenance followed by
child, and remove all the foreign key first which are pointing to this
parent table partition which is going to be dropped by the pg_partman?

As drop/create partition is being called from within pg_partman without our
intervention, so where should we put this drop foreign key code? Do you
mean having that with another event trigger which will fire before drop?

Hi,

Sorry for late reply, I think you will having some script that drops and
creates daily partitions etc, command for disabling/removing any constraint
can be placed before these statements so that when the script runs it does
the needful.

Regards,
Muhammad Ikram
Bitnine global

On Tue, Jul 2, 2024 at 12:54 PM yudhi s <learnerdatabase99@gmail.com> wrote:

On Tue, 2 Jul, 2024, 12:43 pm Muhammad Ikram, <mmikram@gmail.com> wrote:

Hi Yudhi,

I think disabling foreign keys before maintenance will help.

--
Muhammad Ikram

Do you mean to say call the parent table first for maintenance followed by
child, and remove all the foreign key first which are pointing to this
parent table partition which is going to be dropped by the pg_partman?

As drop/create partition is being called from within pg_partman without
our intervention, so where should we put this drop foreign key code? Do you
mean having that with another event trigger which will fire before drop?

--
Muhammad Ikram