Re: Parallel Full Hash Join

Thomas Munro <thomas.munro@gmail.com> writes:
> I committed the main patch.

BTW, it was easy to miss in all the buildfarm noise from
last-possible-minute patches, but chimaera just showed something
that looks like a bug in this code [1]:

2023-04-08 12:25:28.709 UTC [18027:321] pg_regress/join_hash LOG:  statement: savepoint settings;
2023-04-08 12:25:28.709 UTC [18027:322] pg_regress/join_hash LOG:  statement: set local max_parallel_workers_per_gather
=2; 
2023-04-08 12:25:28.710 UTC [18027:323] pg_regress/join_hash LOG:  statement: explain (costs off)
         select  count(*) from simple r full outer join simple s on (r.id = 0 - s.id);
2023-04-08 12:25:28.710 UTC [18027:324] pg_regress/join_hash LOG:  statement: select  count(*) from simple r full outer
joinsimple s on (r.id = 0 - s.id); 
TRAP: failed Assert("BarrierParticipants(&batch->batch_barrier) == 1"), File: "nodeHash.c", Line: 2118, PID: 19147
postgres: parallel worker for PID 18027 (ExceptionalCondition+0x84)[0x10ae2bfa4]
postgres: parallel worker for PID 18027 (ExecParallelPrepHashTableForUnmatched+0x224)[0x10aa67544]
postgres: parallel worker for PID 18027 (+0x3db868)[0x10aa6b868]
postgres: parallel worker for PID 18027 (+0x3c4204)[0x10aa54204]
postgres: parallel worker for PID 18027 (+0x3c81b8)[0x10aa581b8]
postgres: parallel worker for PID 18027 (+0x3b3d28)[0x10aa43d28]
postgres: parallel worker for PID 18027 (standard_ExecutorRun+0x208)[0x10aa39768]
postgres: parallel worker for PID 18027 (ParallelQueryMain+0x2bc)[0x10aa4092c]
postgres: parallel worker for PID 18027 (ParallelWorkerMain+0x660)[0x10a874870]
postgres: parallel worker for PID 18027 (StartBackgroundWorker+0x2a8)[0x10ab8abf8]
postgres: parallel worker for PID 18027 (+0x50290c)[0x10ab9290c]
postgres: parallel worker for PID 18027 (+0x5035e4)[0x10ab935e4]
postgres: parallel worker for PID 18027 (PostmasterMain+0x1304)[0x10ab96334]
postgres: parallel worker for PID 18027 (main+0x86c)[0x10a79daec]

            regards, tom lane

[1] https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=chimaera&dt=2023-04-08%2012%3A07%3A08