RE: Forget close an open relation in ReorderBufferProcessTXN()

On Thursday, April 29, 2021 2:31 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> I am not so sure about it because I think we don't have any example of
> user_catalog_tables in the core code. This is the reason I was kind of looking
> towards Andres to clarify this. Right now, if the user performs TRUNCATE on
> user_catalog_table in synchronous mode then it will hang in case the
> decoding plugin takes even share lock on it. The main reason is that we allow
> decoding of TRUNCATE operation for user_catalog_tables. I think even if we
> want to allow decoding of other operations on user_catalog_table, the
> decoding of TRUNCATE should be prohibited but maybe we shouldn't allow
> decoding of any operation on such tables as we don't do it for system catalog
> tables.

I tried the following scenarios for trying to reproduce this.

Scenario1:
(1) set up 1 publisher and 1 subscriber
(2) create table with user_catalog_table = true on the pub
(3) insert some data to this table
(4) create publication for the table on the pub
(5) create table with user_catalog_table = true on the sub
(6) create subscription on the sub
(7) add synchronous_standby_names to publisher's configuration and restart the pub
(8) have 1 session to hold a lock to the user_catalog_table on the pub in access share mode
(9) have another session to truncate the user_catalog_table on the pub

Here, It keeps waiting but I'm not sure this is the scenario described above,
since this deadlock is caused by (8)'s lock.

Scenario2:
(1) set up 1 publisher and 1 subscriber
(2) create table with user_catalog_table = true on the pub
(3) insert some data to this table
(4) create publication for the table on the pub
(5) create table with user_catalog_table = true on the sub
(6) create subscription on the sub
(7) add synchronous_standby_names to publisher's configuration and restart the pub
(8) have a session to truncate the user_catalog_table on the pub

Scenario 2 was successful.

Are these the scenario you have in mind,
if not please let me know for the missing steps.
I would like to reproduce the scenario and write a patch to fix this.


Best Regards,
	Takamichi Osumi