backend process was crashed when using zabbix monitor

## 1. environmental information
PostgreSQL version: 9.6.8
Operating system:   CentOS 6.9

## 2. problem
When ZABBIX is monitored, the following error message appears in the PG log

    2018-12-24 10:54:33.928 CST 24677     LOG:  server process (PID 13627) was terminated by signal 6: Aborted
    2018-12-24 10:54:33.928 CST 24677     DETAIL:  Failed process was running: select sum(calls) as sum_calls from pg_stat_statements
    2018-12-24 10:54:33.928 CST 24677     LOG:  terminating any other active server processes

## 3. Occurrence condition
SQL was executed in ZABBIX monitoring：select sum(calls) as sum_calls from pg_stat_statements

## 4. invest
### The similar report
https://www.postgresql.org/message-id/1935021523893352%40web12o.yandex.ru

### stacktrace
[root(at)sndsdevsdd01 crash_20181224]# gdb /usr/pgsql-10/bin/postgres core.postgres.1545620056.13627
GNU gdb (GDB) Red Hat Enterprise Linux (7.2-56.el6)
Copyright (C) 2010 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html&gt;
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.&nbsp; Type "show copying"and "show warranty" for details.
This GDB was configured as "x86_64-redhat-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/&gt;...
Reading symbols from /usr/pgsql-10/bin/postgres...Reading symbols from /usr/lib/debug/usr/pgsql-10/bin/postgres.debug...done.
done.
[New Thread 13627]
Missing separate debuginfo for
Try: yum --disablerepo='*' --enablerepo='*-debug*' install /usr/lib/debug/.build-id/37/7408871ceed5b3282b8fc1d771a14fec2a7cc7
Reading symbols from /lib64/libpthread.so.0...(no debugging symbols found)...done.
[Thread debugging using libthread_db enabled]
...Core was generated by `postgres: monitor lobadbt1'.
Program terminated with signal 6, Aborted.
#0&nbsp; 0x000000369e232625 in raise () from /lib64/libc.so.6
Missing separate debuginfos, use: debuginfo-install audit-libs-2.2-2.el6.x86_64 cyrus-sasl-lib-2.1.23-13.el6.x86_64 glibc-2.12-1.166.el6_7.7.x86_64 keyutils-libs-1.4-4.el6.x86_64 krb5-libs-1.9-33.el6.x86_64 libcom_err-1.41.12-12.el6.x86_64 libcurl-7.19.7-26.el6_2.4.x86_64 libgcc-4.4.6-4.el6.x86_64 libicu-4.2.1-9.1.el6_2.x86_64 libidn-1.18-2.el6.x86_64 libselinux-2.0.94-5.3.el6.x86_64 libssh2-1.2.2-7.el6_2.3.x86_64 libstdc++-4.4.6-4.el6.x86_64 libxml2-2.7.6-4.el6_2.4.x86_64 nspr-4.9-1.el6.x86_64 nss-3.13.3-6.el6.x86_64 nss-softokn-freebl-3.12.9-11.el6.x86_64 nss-util-3.13.3-2.el6.x86_64 openldap-2.4.23-26.el6.x86_64 openssl-1.0.1e-42.el6_7.4.x86_64 pam-1.1.1-10.el6_2.1.x86_64 zlib-1.2.3-27.el6.x86_64
(gdb) bt
#0&nbsp; 0x000000369e232625 in raise () from /lib64/libc.so.6
#1&nbsp; 0x000000369e233e05 in abort () from /lib64/libc.so.6
#2&nbsp; 0x000000369e270537 in __libc_message () from /lib64/libc.so.6
#3&nbsp; 0x000000369e275f4e in malloc_printerr () from /lib64/libc.so.6
#4&nbsp; 0x000000369e278cf0 in _int_free () from /lib64/libc.so.6
#5&nbsp; 0x0000000000858ab7 in tuplestore_end (state=0x2b6cee0) at tuplestore.c:458#6&nbsp; 0x00000000006088a5 in ExecEndFunctionScan (node=0x2b48d00) at nodeFunctionscan.c:550
#7&nbsp; 0x00000000005f7c9e in ExecEndPlan (queryDesc=<value optimized out&gt;) at execMain.c:1606
#8&nbsp; standard_ExecutorEnd (queryDesc=<value optimized out&gt;) at execMain.c:495
#9&nbsp; 0x00000000005af67e in PortalCleanup (portal=0x2a68e08) at portalcmds.c:302
#10 0x000000000084d19a in PortalDrop (portal=0x2a68e08, isTopCommit=0 '\000') at portalmem.c:489
#11 0x0000000000723f62 in exec_simple_query (
&nbsp;&nbsp;&nbsp; query_string=0x2a29ef8 "select sum(calls) as sum_calls from pg_stat_statements") at postgres.c:1109
#12 0x0000000000724f09 in PostgresMain (argc=<value optimized out&gt;, argv=<value optimized out&gt;, dbname=0x29b7960 "lobadbt1", username=<value optimized out&gt;) at postgres.c:4088
#13 0x00000000006b8c8a in BackendRun (argc=<value optimized out&gt;, argv=<value optimized out&gt;) at postmaster.c:4405
#14 BackendStartup (argc=<value optimized out&gt;, argv=<value optimized out&gt;) at postmaster.c:4077
#15 ServerLoop (argc=<value optimized out&gt;, argv=<value optimized out&gt;) at postmaster.c:1755
#16 PostmasterMain (argc=<value optimized out&gt;, argv=<value optimized out&gt;) at postmaster.c:1363
#17 0x00000000006395e0 in main (argc=1, argv=0x29739e0) at main.c:228
(gdb) f 5
#5&nbsp; 0x0000000000858ab7 in tuplestore_end (state=0x2b6cee0) at tuplestore.c:458
458 BufFileClose(state-&gt;myfile);
(gdb) p state-&gt;myfile$1 = (BufFile *) 0x74e1a68
(gdb) p *state-&gt;myfile
$2 = {numFiles = 1, files = 0x587d0a8, offsets = 0x5564668, isTemp = 1 '\001', isInterXact = 0 '\000',
&nbsp; dirty = 0 '\000', resowner = 0x2974e68, curFile = 0, curOffset = 42890164, pos = 0, nbytes = 0,
&nbsp; buffer = "152958850543,20181222153019086124,20181222153127806225,20181222153158113565,20181222153317920155,20181222153437816384,20181222153640243830,20181222153758325087,20181227,2018122215383582234"...}
(gdb) p debug_query_string
$3 = 0x2a29ef8 "select sum(calls) as sum_calls from pg_stat_statements"
(gdb)