Windows 10
MS VS 2015
MongoDB 3.3.5
MongoDB C++11 Driver 3.0.1
Using WiredTiger

I want the statistic

"btree" { "number of key/value pairs"}

which is equal to "btree_entries" from bt_stat.c. (I recognize this is "really, really expensive").

I run this in mongo:

db.adminCommand({ setParameter: 1, "wiredTigerEngineRuntimeConfig" : "create,statistics=(all)"})

and mongod reports it was successful:

2016-08-17T11:18:00.960-0700 I STORAGE  [conn5176] Reconfiguring WiredTiger storage engine with config string: "statistics=(all)"

which, presumably, sets WT_CONN_STAT_ALL so that btree_entries will be collected.

According to the documentation, I have to use the db.adminCommand. "You can only set this parameter using the setParameter command and not using the command line or configuration file option."

But when I then run:

db.employees.stats({'indexDetails':true, 'indexDetailsName': "employeenum_1_check_1"})

I still get:

"number of key/value pairs" : 0,