irb.rb

def client(db_name = 'postgres')
    PG::Connection.connect( port: 6432, user: 'postgres',  dbname: 'postgres')
end


def client2(db_name = 'postgres')
    PG::Connection.connect( port: 6432, user: 'postgres',  dbname: 'postgres')
end

def client3(db_name = 'postgres')
    PG::Connection.connect( port: 6432, user: 'postgres',  dbname: 'postgres')
end

def client4(db_name = 'postgres')
    PG::Connection.connect( port: 6432, user: 'postgres',  dbname: 'postgres')
end

def client5(db_name = 'postgres')
    PG::Connection.connect( port: 6432, user: 'postgres',  dbname: 'postgres')
end

client.exec(" SELECT pg_database.datname FROM pg_database WHERE datistemplate = false")
client2.exec(" SELECT pg_database.datname FROM pg_database WHERE datistemplate = false")
client3.exec(" SELECT pg_database.datname FROM pg_database WHERE datistemplate = false")
client4.exec(" SELECT pg_database.datname FROM pg_database WHERE datistemplate = false")

c = client; c.close
c = client2; c.close
c= client3; c.close
c= client4; c.close

postgres.sql

select * from pg_stat_activity where datname = 'postgres' and (state='idle' or state='active')

> 4