Re: [HACKERS] BUG #13473: VACUUM FREEZE mistakenly cancel standby sessions

On 27/06/15 01:13, Jim Nasby wrote:
> On 6/26/15 8:50 AM, Marco Nenciarini wrote:
>>> >In the heap_xlog_freeze we need to subtract one to the value of
>>> cutoff_xid
>>> >before passing it to ResolveRecoveryConflictWithSnapshot.
>>> >
>>> >
>>> >
>> Attached a proposed patch that solves the issue.
>

I have hit the bug again, as it has been fixed only from 9.5+

The procedure to reproduce it sent in the original post is not fully
accurate, below there is one that always works:

Run the following operation on an idle cluster.

1) connect to the master and run the following script

create table t(id int primary key);
insert into t select generate_series(1, 10000);

2) connect to the standby and simulate a long running query:

select pg_sleep(3600);

3) on the master and run the following commands:
vacuum freeze verbose t;
drop table t;

4) after 30 seconds the pg_sleep query on standby will be canceled.

Attached there is a patch that apply on every version that misses the
fix (9.0, 9.1, 9.2, 9.3, 9.4)

Regards,
Marco

--
Marco Nenciarini - 2ndQuadrant Italy
PostgreSQL Training, Services and Support
marco(dot)nenciarini(at)2ndQuadrant(dot)it | www.2ndQuadrant.it