live and dead tuples are zero on slave running on tmpfs

Hello,

I have a master slave (read replica) setup running pg 9.4.4. I'm
trying to find the dead tuples out both the master and slave

Here's what it looks like on master:

# select relname ,n_live_tup ,n_dead_tup from pg_stat_user_tables;
relname | n_live_tup | n_dead_tup
------------------+------------+------------
test_52 | 4998366 | 0
test_v2 | 25182728 | 4086591
test_1mrows | 1000127 | 0

That seems legit because I did an update to ~4million rows just before this.

Here's what it looks on slave though

#select relname ,n_live_tup ,n_dead_tup from pg_stat_user_tables;
relname | n_live_tup | n_dead_tup
------------------+------------+------------
test_52 | 0 | 0
test_v2 | 0 | 0
test_1mrows | 0 | 0

the postgres data directory on the slave is configured to a tmpfs
mounted store. Would this cause it to have zero live & dead tuples ?

postgres version on master and slave:
PostgreSQL 9.4.4 on x86_64-unknown-linux-gnu, compiled by gcc (Ubuntu
4.8.2-19ubuntu1) 4.8.2, 64-bit

-- Karthik