Re: [HACKERS] Issues with logical replication

On 02/10/17 18:59, Petr Jelinek wrote:
>>
>> Now fix the trigger function:
>> CREATE OR REPLACE FUNCTION replication_trigger_proc() RETURNS TRIGGER AS $$
>> BEGIN
>>   RETURN NEW;
>> END $$ LANGUAGE plpgsql;
>>
>> And manually perform at master two updates inside one transaction:
>>
>> postgres=# begin;
>> BEGIN
>> postgres=# update pgbench_accounts set abalance=abalance+1 where aid=26;
>> UPDATE 1
>> postgres=# update pgbench_accounts set abalance=abalance-1 where aid=26;
>> UPDATE 1
>> postgres=# commit;
>> <hangs>
>>
>> and in replica log we see:
>> 2017-10-02 18:40:26.094 MSK [2954] LOG:  logical replication apply
>> worker for subscription "sub" has started
>> 2017-10-02 18:40:26.101 MSK [2954] ERROR:  attempted to lock invisible
>> tuple
>> 2017-10-02 18:40:26.102 MSK [2882] LOG:  worker process: logical
>> replication worker for subscription 16403 (PID 2954) exited with exit
>> code 1
>>
>> Error happens in trigger.c:
>>
>> #3  0x000000000069bddb in GetTupleForTrigger (estate=0x2e36b50,
>> epqstate=0x7ffc4420eda0, relinfo=0x2dcfe90, tid=0x2dd08ac,
>>     lockmode=LockTupleNoKeyExclusive, newSlot=0x7ffc4420ec40) at
>> trigger.c:3103
>> #4  0x000000000069b259 in ExecBRUpdateTriggers (estate=0x2e36b50,
>> epqstate=0x7ffc4420eda0, relinfo=0x2dcfe90, tupleid=0x2dd08ac,
>>     fdw_trigtuple=0x0, slot=0x2dd0240) at trigger.c:2748
>> #5  0x00000000006d2395 in ExecSimpleRelationUpdate (estate=0x2e36b50,
>> epqstate=0x7ffc4420eda0, searchslot=0x2dd0358, slot=0x2dd0240)
>>     at execReplication.c:461
>> #6  0x0000000000820894 in apply_handle_update (s=0x7ffc442163b0) at
>> worker.c:736
> 
> We have locked the same tuple in RelationFindReplTupleByIndex() just
> before this gets called and didn't get the same error. I guess we do
> something wrong with snapshots. Will need to investigate more.
> 

Okay, so it's not snapshot. It's the fact that we don't set the
es_output_cid in replication worker which GetTupleForTrigger is using
when locking the tuple. Attached one-liner fixes it.

-- 
  Petr Jelinek                  http://www.2ndQuadrant.com/
  PostgreSQL Development, 24x7 Support, Training & Services

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