Hi > Here's confirmed steps to reproduce
Wow, i confirm this testcase is reproducible for me. On my 4-core desktop i see "dsa_area could not attach to segment" error after minute or two. On current REL_11_STABLE branch with PANIC level i see this backtrace for failed parallel process: #0 __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50 #1 0x00007f3b36983535 in __GI_abort () at abort.c:79 #2 0x000055f03ab87a4e in errfinish (dummy=dummy@entry=0) at elog.c:555 #3 0x000055f03ab899e0 in elog_finish (elevel=elevel@entry=22, fmt=fmt@entry=0x55f03ad86900 "dsa_area could not attach to segment") at elog.c:1376 #4 0x000055f03abaa1e2 in get_segment_by_index (area=area@entry=0x55f03cdd6bf0, index=index@entry=7) at dsa.c:1743 #5 0x000055f03abaa8ab in get_best_segment (area=area@entry=0x55f03cdd6bf0, npages=npages@entry=8) at dsa.c:1993 #6 0x000055f03ababdb8 in dsa_allocate_extended (area=0x55f03cdd6bf0, size=size@entry=32768, flags=flags@entry=0) at dsa.c:701 #7 0x000055f03a921469 in ExecParallelHashTupleAlloc (hashtable=hashtable@entry=0x55f03cdfd498, size=104, shared=shared@entry=0x7ffc9f355748) at nodeHash.c:2837 #8 0x000055f03a9219fc in ExecParallelHashTableInsertCurrentBatch (hashtable=hashtable@entry=0x55f03cdfd498, slot=<optimized out>, hashvalue=2522126815) at nodeHash.c:1747 #9 0x000055f03a9227ef in ExecParallelHashJoinNewBatch (hjstate=hjstate@entry=0x55f03cde17b0) at nodeHashjoin.c:1153 #10 0x000055f03a924115 in ExecHashJoinImpl (parallel=true, pstate=0x55f03cde17b0) at nodeHashjoin.c:534 #11 ExecParallelHashJoin (pstate=0x55f03cde17b0) at nodeHashjoin.c:581 #12 0x000055f03a90d91c in ExecProcNodeFirst (node=0x55f03cde17b0) at execProcnode.c:445 #13 0x000055f03a905f3b in ExecProcNode (node=0x55f03cde17b0) at ../../../src/include/executor/executor.h:247 #14 ExecutePlan (estate=estate@entry=0x55f03cde0d38, planstate=0x55f03cde17b0, use_parallel_mode=<optimized out>, operation=operation@entry=CMD_SELECT, sendTuples=sendTuples@entry=true, numberTuples=numberTuples@entry=0, direction=ForwardScanDirection, dest=0x55f03cd7e4e8, execute_once=true) at execMain.c:1723 #15 0x000055f03a906b4d in standard_ExecutorRun (queryDesc=0x55f03cdd13e0, direction=ForwardScanDirection, count=0, execute_once=execute_once@entry=true) at execMain.c:364 #16 0x000055f03a906c08 in ExecutorRun (queryDesc=queryDesc@entry=0x55f03cdd13e0, direction=direction@entry=ForwardScanDirection, count=<optimized out>, execute_once=execute_once@entry=true) at execMain.c:307 #17 0x000055f03a90b44f in ParallelQueryMain (seg=seg@entry=0x55f03cd320a8, toc=toc@entry=0x7f3b2d877000) at execParallel.c:1402 #18 0x000055f03a7ce4cc in ParallelWorkerMain (main_arg=<optimized out>) at parallel.c:1409 #19 0x000055f03a9e11cb in StartBackgroundWorker () at bgworker.c:834 #20 0x000055f03a9eea1a in do_start_bgworker (rw=rw@entry=0x55f03cd2d460) at postmaster.c:5698 #21 0x000055f03a9eeb5b in maybe_start_bgworkers () at postmaster.c:5911 #22 0x000055f03a9ef5f0 in sigusr1_handler (postgres_signal_arg=<optimized out>) at postmaster.c:5091 #23 <signal handler called> #24 0x00007f3b36a52327 in __GI___select (nfds=nfds@entry=6, readfds=readfds@entry=0x7ffc9f356160, writefds=writefds@entry=0x0, exceptfds=exceptfds@entry=0x0, timeout=timeout@entry=0x7ffc9f356150) at ../sysdeps/unix/sysv/linux/select.c:41 #25 0x000055f03a9effaa in ServerLoop () at postmaster.c:1670 #26 0x000055f03a9f1285 in PostmasterMain (argc=3, argv=<optimized out>) at postmaster.c:1379 #27 0x000055f03a954f3d in main (argc=3, argv=0x55f03cd03200) at main.c:228 regards, Sergei