Server crash in pg_replication_slot_advance function

Hi,

While playing around with newly implemented function
'pg_replication_slot_advance' , found a server crash .

Please refer the testcase scenario -

centos(at)centos-cpula bin]$ ./psql  postgres
psql (11devel)
Type "help" for help.

postgres=#  SELECT * FROM
pg_create_logical_replication_slot('regression_slot1', 'test_decoding',
true);
    slot_name     |    lsn
------------------+-----------
 regression_slot1 | 0/1636AE8
(1 row)

postgres=# select * from pg_replication_slots;
    slot_name     |    plugin     | slot_type | datoid | database |
temporary | active | active_pid | xmin | catalog_xmin | restart_lsn |
confirmed_flush_lsn
------------------+---------------+-----------+--------+----------+-----------+--------+------------+------+--------------+-------------+---------------------
 regression_slot1 | test_decoding | logical   |  13220 | postgres |
t         | t      |      25910 |      |          557 | 0/1636AB0 |
0/1636AE8
(1 row)

postgres=# select pg_switch_wal();
 pg_switch_wal
---------------
 0/1636B38
(1 row)

postgres=# select pg_switch_wal();
 pg_switch_wal
---------------
 0/2000078
(1 row)

postgres=# SELECT end_lsn FROM
pg_replication_slot_advance('regression_slot1', '0/2000078');
  end_lsn
-----------
 0/2000078
(1 row)

postgres=# select * from pg_replication_slots;
2018-02-16 08:09:57.989 GMT [25910] LOG:  statement: select * from
pg_replication_slots;
    slot_name     |    plugin     | slot_type | datoid | database |
temporary | active | active_pid | xmin | catalog_xmin | restart_lsn |
confirmed_flush_lsn
------------------+---------------+-----------+--------+----------+-----------+--------+------------+------+--------------+-------------+---------------------
 regression_slot1 | test_decoding | logical   |  13220 | postgres |
t         | t      |      25910 |      |          557 | 0/2000028 |
0/2000078
(1 row)

postgres=# SELECT end_lsn FROM
pg_replication_slot_advance('regression_slot1', '0/2000071');
server closed the connection unexpectedly
This probably means the server terminated abnormally
 before or while processing the request.
!>

Stack trace -

Core was generated by `postgres: centos postgres [local]
SELECT                      '.
Program terminated with signal 11, Segmentation fault.
#0  0x00000000008519a8 in pg_replication_slot_advance
(fcinfo=0x7fff5c9c4630) at slotfuncs.c:479
479            ereport(ERROR,
Missing separate debuginfos, use: debuginfo-install
glibc-2.12-1.192.el6.x86_64 keyutils-libs-1.4-5.el6.x86_64
krb5-libs-1.10.3-57.el6.x86_64 libcom_err-1.41.12-22.el6.x86_64
libselinux-2.0.94-7.el6.x86_64 openssl-1.0.1e-48.el6_8.4.x86_64
zlib-1.2.3-29.el6.x86_64
(gdb) bt
#0  0x00000000008519a8 in pg_replication_slot_advance
(fcinfo=0x7fff5c9c4630) at slotfuncs.c:479
#1  0x00000000006defdc in ExecMakeTableFunctionResult
(setexpr=0x20f7db0, econtext=0x20f7aa8, argContext=0x20fd690,
expectedDesc=0x20f92d0, randomAccess=0 '\000') at execSRF.c:231
#2  0x00000000006f1782 in FunctionNext (node=0x20f7990) at
nodeFunctionscan.c:95
#3  0x00000000006de80d in ExecScanFetch (node=0x20f7990,
accessMtd=0x6f16cb <FunctionNext>, recheckMtd=0x6f1abd
<FunctionRecheck>) at execScan.c:95
#4  0x00000000006de8ad in ExecScan (node=0x20f7990, accessMtd=0x6f16cb
<FunctionNext>, recheckMtd=0x6f1abd <FunctionRecheck>) at execScan.c:162
#5  0x00000000006f1b0a in ExecFunctionScan (pstate=0x20f7990) at
nodeFunctionscan.c:270
#6  0x00000000006dcd66 in ExecProcNodeFirst (node=0x20f7990) at
execProcnode.c:446
#7  0x00000000006d3c05 in ExecProcNode (node=0x20f7990) at
../../../src/include/executor/executor.h:246
#8  0x00000000006d6559 in ExecutePlan (estate=0x20f7778,
planstate=0x20f7990, use_parallel_mode=0 '\000', operation=CMD_SELECT,
sendTuples=1 '\001', numberTuples=0,
    direction=ForwardScanDirection, dest=0x20fd288, execute_once=1
'\001') at execMain.c:1721
#9  0x00000000006d41d7 in standard_ExecutorRun (queryDesc=0x2065878,
direction=ForwardScanDirection, count=0, execute_once=1 '\001') at
execMain.c:361
#10 0x00000000006d3ff3 in ExecutorRun (queryDesc=0x2065878,
direction=ForwardScanDirection, count=0, execute_once=1 '\001') at
execMain.c:304
#11 0x00000000008afeeb in PortalRunSelect (portal=0x20a5838, forward=1
'\001', count=0, dest=0x20fd288) at pquery.c:932
#12 0x00000000008afb79 in PortalRun (portal=0x20a5838,
count=9223372036854775807, isTopLevel=1 '\001', run_once=1 '\001',
dest=0x20fd288, altdest=0x20fd288,
    completionTag=0x7fff5c9c4f00 "") at pquery.c:773
#13 0x00000000008a9ba0 in exec_simple_query (query_string=0x2040438
"SELECT end_lsn FROM pg_replication_slot_advance('regression_slot1',
'0/2000071');") at postgres.c:1120
#14 0x00000000008ade34 in PostgresMain (argc=1, argv=0x206bec0,
dbname=0x206bd20 "postgres", username=0x203cf58 "centos") at postgres.c:4144
#15 0x000000000080d11a in BackendRun (port=0x2063d00) at postmaster.c:4412
#16 0x000000000080c88e in BackendStartup (port=0x2063d00) at
postmaster.c:4084
#17 0x0000000000808cbb in ServerLoop () at postmaster.c:1757
#18 0x0000000000808379 in PostmasterMain (argc=3, argv=0x203aeb0) at
postmaster.c:1365
#19 0x000000000073d3d0 in main (argc=3, argv=0x203aeb0) at main.c:228
(gdb)

--
regards,tushar
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