Re: Parallel Full Hash Join

> Rebased patches attached. I will change status back to "Ready for Committer"

The CI showed a crash on freebsd, which I reproduced.
https://cirrus-ci.com/task/5203060415791104

The crash is evidenced in 0001 - but only ~15% of the time.

I think it's the same thing which was committed and then reverted here, so
maybe I'm not saying anything new.

https://commitfest.postgresql.org/33/3031/
https://www.postgresql.org/message-id/flat/20200929061142.GA29096@paquier.xyz

(gdb) p pstate->build_barrier->phase 
Cannot access memory at address 0x7f82e0fa42f4

#1  0x00007f13de34f801 in __GI_abort () at abort.c:79
#2  0x00005638e6a16d28 in ExceptionalCondition (conditionName=conditionName@entry=0x5638e6b62850 "!pstate || BarrierPhase(&pstate->build_barrier) >= PHJ_BUILD_RUN",
    errorType=errorType@entry=0x5638e6a6f00b "FailedAssertion", fileName=fileName@entry=0x5638e6b625be "nodeHash.c", lineNumber=lineNumber@entry=3305) at assert.c:69
#3  0x00005638e678085b in ExecHashTableDetach (hashtable=0x5638e8e6ca88) at nodeHash.c:3305
#4  0x00005638e6784656 in ExecShutdownHashJoin (node=node@entry=0x5638e8e57cb8) at nodeHashjoin.c:1400
#5  0x00005638e67666d8 in ExecShutdownNode (node=0x5638e8e57cb8) at execProcnode.c:812
#6  ExecShutdownNode (node=0x5638e8e57cb8) at execProcnode.c:772
#7  0x00005638e67cd5b1 in planstate_tree_walker (planstate=planstate@entry=0x5638e8e58580, walker=walker@entry=0x5638e6766680 <ExecShutdownNode>, context=context@entry=0x0) at nodeFuncs.c:4009
#8  0x00005638e67666b2 in ExecShutdownNode (node=0x5638e8e58580) at execProcnode.c:792
#9  ExecShutdownNode (node=0x5638e8e58580) at execProcnode.c:772
#10 0x00005638e67cd5b1 in planstate_tree_walker (planstate=planstate@entry=0x5638e8e58418, walker=walker@entry=0x5638e6766680 <ExecShutdownNode>, context=context@entry=0x0) at nodeFuncs.c:4009
#11 0x00005638e67666b2 in ExecShutdownNode (node=0x5638e8e58418) at execProcnode.c:792
#12 ExecShutdownNode (node=node@entry=0x5638e8e58418) at execProcnode.c:772
#13 0x00005638e675f518 in ExecutePlan (execute_once=<optimized out>, dest=0x5638e8df0058, direction=<optimized out>, numberTuples=0, sendTuples=<optimized out>, operation=CMD_SELECT,
    use_parallel_mode=<optimized out>, planstate=0x5638e8e58418, estate=0x5638e8e57a10) at execMain.c:1658
#14 standard_ExecutorRun () at execMain.c:410
#15 0x00005638e6763e0a in ParallelQueryMain (seg=0x5638e8d823d8, toc=0x7f13df4e9000) at execParallel.c:1493
#16 0x00005638e663f6c7 in ParallelWorkerMain () at parallel.c:1495
#17 0x00005638e68542e4 in StartBackgroundWorker () at bgworker.c:858
#18 0x00005638e6860f53 in do_start_bgworker (rw=<optimized out>) at postmaster.c:5883
#19 maybe_start_bgworkers () at postmaster.c:6108
#20 0x00005638e68619e5 in sigusr1_handler (postgres_signal_arg=<optimized out>) at postmaster.c:5272
#21 <signal handler called>
#22 0x00007f13de425ff7 in __GI___select (nfds=nfds@entry=7, readfds=readfds@entry=0x7ffef03b8400, writefds=writefds@entry=0x0, exceptfds=exceptfds@entry=0x0, timeout=timeout@entry=0x7ffef03b8360)
    at ../sysdeps/unix/sysv/linux/select.c:41
#23 0x00005638e68620ce in ServerLoop () at postmaster.c:1765
#24 0x00005638e6863bcc in PostmasterMain () at postmaster.c:1473
#25 0x00005638e658fd00 in main (argc=8, argv=0x5638e8d54730) at main.c:198