pgtest02f/postgres R # show shared_preload_libraries ;
                shared_preload_libraries
---------------------------------------------------------
 pg_stat_statements,pg_stat_kcache,pg_stat_wait,repl_mon
(1 row)

Time: 0.366 ms
pgtest02f/postgres R # select pg_is_in_recovery();
 pg_is_in_recovery
-------------------
 t
(1 row)

Time: 0.715 ms
pgtest02f/postgres R # select * from pg_stat_wait_current ;
  pid  |           sample_ts           | class_id | class_name | event_id | event_name | wait_time | p1 | p2 | p3 | p4 | p5
-------+-------------------------------+----------+------------+----------+------------+-----------+----+----+----+----+----
 28182 | 2015-07-08 11:56:18.611896+03 |        4 | Latch      |        0 | Latch      |    841512 |  0 |  0 |  0 |  0 |  0
 28260 | 2015-07-08 11:56:18.611896+03 |        4 | Latch      |        0 | Latch      |     33178 |  0 |  0 |  0 |  0 |  0
 28259 | 2015-07-08 11:56:18.611896+03 |        4 | Latch      |        0 | Latch      |  29602538 |  0 |  0 |  0 |  0 |  0
 28270 | 2015-07-08 11:56:18.611896+03 |        5 | Network    |        0 | READ       |    763131 |  0 |  0 |  0 |  0 |  0
 28266 | 2015-07-08 11:56:18.611896+03 |        5 | Network    |        0 | READ       |    425323 |  0 |  0 |  0 |  0 |  0
(5 rows)

Time: 5.924 ms
pgtest02f/postgres R # select * from pg_stat_wait_history ;
server closed the connection unexpectedly
    This probably means the server terminated abnormally
    before or while processing the request.
The connection to the server was lost. Attempting reset: Failed.
Time: 831.582 ms
psql: server closed the connection unexpectedly
    This probably means the server terminated abnormally
    before or while processing the request.
pgtest02f/ R >

(gdb) bt
#0  SetLatch (latch=0x0) at pg_latch.c:518
#1  0x00007f99c51a8b73 in pg_stat_wait_get_history (fcinfo=0x7ffffedff180) at pg_stat_wait.c:558
#2  0x000000000059ed67 in ExecMakeTableFunctionResult (funcexpr=0x161c630, econtext=0x161be58, argContext=<value optimized out>, expectedDesc=0x161d9e8, randomAccess=0 '\000') at execQual.c:2196
#3  0x00000000005b07f2 in FunctionNext (node=0x161bd48) at nodeFunctionscan.c:95
#4  0x000000000059f94e in ExecScanFetch (node=0x161bd48, accessMtd=0x5b0540 <FunctionNext>, recheckMtd=0x5afe70 <FunctionRecheck>) at execScan.c:82
#5  ExecScan (node=0x161bd48, accessMtd=0x5b0540 <FunctionNext>, recheckMtd=0x5afe70 <FunctionRecheck>) at execScan.c:132
#6  0x0000000000598878 in ExecProcNode (node=0x161bd48) at execProcnode.c:426
#7  0x00000000005b1c19 in ExecSort (node=0x161bad8) at nodeSort.c:103
#8  0x00000000005987e8 in ExecProcNode (node=0x161bad8) at execProcnode.c:468
#9  0x00000000005adc68 in ExecMergeJoin (node=0x15f0a00) at nodeMergejoin.c:730
#10 0x0000000000598818 in ExecProcNode (node=0x15f0a00) at execProcnode.c:453
#11 0x00000000005973e2 in ExecutePlan (queryDesc=0x15f3f90, direction=<value optimized out>, count=0) at execMain.c:1490
#12 standard_ExecutorRun (queryDesc=0x15f3f90, direction=<value optimized out>, count=0) at execMain.c:319
#13 0x00007f99c55b317b in pgss_ExecutorRun (queryDesc=0x15f3f90, direction=ForwardScanDirection, count=0) at pg_stat_statements.c:875
#14 0x000000000068c2d7 in PortalRunSelect (portal=0x1505c10, forward=<value optimized out>, count=0, dest=<value optimized out>) at pquery.c:946
#15 0x000000000068d501 in PortalRun (portal=0x1505c10, count=9223372036854775807, isTopLevel=1 '\001', dest=0x1652f50, altdest=0x1652f50, completionTag=0x7ffffedffa70 "") at pquery.c:790
#16 0x0000000000689b8e in exec_simple_query (query_string=0x14f8f80 "select * from pg_stat_wait_history ;") at postgres.c:1072
#17 0x000000000068b208 in PostgresMain (argc=<value optimized out>, argv=<value optimized out>, dbname=0x14df980 "postgres", username=<value optimized out>) at postgres.c:4074
#18 0x0000000000633fdd in BackendRun (argc=<value optimized out>, argv=<value optimized out>) at postmaster.c:4164
#19 BackendStartup (argc=<value optimized out>, argv=<value optimized out>) at postmaster.c:3829
#20 ServerLoop (argc=<value optimized out>, argv=<value optimized out>) at postmaster.c:1597
#21 PostmasterMain (argc=<value optimized out>, argv=<value optimized out>) at postmaster.c:1244
#22 0x00000000005cbc28 in main (argc=3, argv=0x14deaa0) at main.c:228
(gdb)