* thread #13: tid = 21761, 0x00007fa0cea8104f libc.so.6`__GI_raise + 207, name = 'mserver5', stop reason = signal SIGABRT
    frame #0: 0x00007fa0cea8104f libc.so.6`__GI_raise + 207
libc.so.6`__GI_raise:
->  0x7fa0cea8104f <+207>: addq   $0x88, %rsp
    0x7fa0cea81056 <+214>: movl   %r8d, %eax
    0x7fa0cea81059 <+217>: popq   %rbx
    0x7fa0cea8105a <+218>: retq   
(lldb) bt
* thread #13: tid = 21761, 0x00007fa0cea8104f libc.so.6`__GI_raise + 207, name = 'mserver5', stop reason = signal SIGABRT
  * frame #0: 0x00007fa0cea8104f libc.so.6`__GI_raise + 207
    frame #1: 0x00007fa0cea8247a libc.so.6`__GI_abort + 362
    frame #2: 0x00007fa0cea79ea7 libc.so.6`__assert_fail_base + 279
    frame #3: 0x00007fa0cea79f52 libc.so.6`__GI___assert_fail + 66
    frame #4: 0x00007fa0cce05c4a lib_sql.so`rel_rename_exps(sql=0x00007fa0a800ea80, exps1=0x00007fa0a80cee10, exps2=0x00007fa0a80d16a0) + 431 at rel_optimizer.c:1798
    frame #5: 0x00007fa0cce12f9b lib_sql.so`rel_push_project_down_union(changes=0x00007fa0c6d70a08, sql=0x00007fa0a800ea80, rel=0x00007fa0a80cf750) + 897 at rel_optimizer.c:4641
    frame #6: 0x00007fa0cce2238d lib_sql.so`rewrite_topdown(sql=0x00007fa0a800ea80, rel=0x00007fa0a80cf750, rewriter=(lib_sql.so`rel_push_project_down_union at rel_optimizer.c:4609), has_changes=0x00007fa0c6d70a08) + 76 at rel_optimizer.c:8305
    frame #7: 0x00007fa0cce224c0 lib_sql.so`rewrite_topdown(sql=0x00007fa0a800ea80, rel=0x00007fa0a80cf850, rewriter=(lib_sql.so`rel_push_project_down_union at rel_optimizer.c:4609), has_changes=0x00007fa0c6d70a08) + 383 at rel_optimizer.c:8334
    frame #8: 0x00007fa0cce22d22 lib_sql.so`_rel_optimizer(sql=0x00007fa0a800ea80, rel=0x00007fa0a80cf850, level=0) + 1927 at rel_optimizer.c:8492
    frame #9: 0x00007fa0cce22f28 lib_sql.so`rel_optimizer(sql=0x00007fa0a800ea80, rel=0x00007fa0a80cf850) + 55 at rel_optimizer.c:8530
    frame #10: 0x00007fa0ccd12df4 lib_sql.so`sql_symbol2relation(c=0x00007fa0a800ea80, sym=0x00007fa0a80c5c70) + 94 at sql.c:121
    frame #11: 0x00007fa0ccd37efa lib_sql.so`SQLparser(c=0x00007fa0cd396630) + 3677 at sql_scenario.c:1077
    frame #12: 0x00007fa0d1b46c65 libmonetdb5.so.21`runPhase(c=0x00007fa0cd396630, phase=1) + 122 at mal_scenario.c:517
    frame #13: 0x00007fa0d1b46da9 libmonetdb5.so.21`runScenarioBody(c=0x00007fa0cd396630) + 288 at mal_scenario.c:550
    frame #14: 0x00007fa0d1b46f4c libmonetdb5.so.21`runScenario(c=0x00007fa0cd396630) + 76 at mal_scenario.c:579
    frame #15: 0x00007fa0d1b48a92 libmonetdb5.so.21`MSserveClient(dummy=0x00007fa0cd396630) + 488 at mal_session.c:448
    frame #16: 0x00007fa0d1b4853c libmonetdb5.so.21`MSscheduleClient(command="\x80$\f\xa8\xa0\x7f", challenge="Ch6i1CmPe", fin=0x00007fa0a80069e0, fout=0x00007fa0b8007030) + 3472 at mal_session.c:339
    frame #17: 0x00007fa0d1be7e60 libmonetdb5.so.21`doChallenge(data=0x00007fa0b80008d0) + 1209 at mal_mapi.c:197
    frame #18: 0x00007fa0d1649d36 libbat.so.13`thread_starter(arg=0x00007fa0b8009120) + 68 at gdk_system.c:485
    frame #19: 0x00007fa0cedf5454 libpthread.so.0`start_thread + 196
    frame #20: 0x00007fa0ceb367df libc.so.6`__GI___clone + 95
(lldb) frame select 4
frame #4: 0x00007fa0cce05c4a lib_sql.so`rel_rename_exps(sql=0x00007fa0a800ea80, exps1=0x00007fa0a80cee10, exps2=0x00007fa0a80d16a0) + 431 at rel_optimizer.c:1798
   1795			}
   1796		}
   1797	
-> 1798		assert(list_length(exps1) == list_length(exps2)); 
   1799		for (n = exps1->h, m = exps2->h; n && m; n = n->next, m = m->next) {
   1800			sql_exp *e1 = n->data;
   1801			sql_exp *e2 = m->data;