Improve RAM usage allowance

Queries can spawn more processed and then use more RAM than
`shared_buffers`

site-cookbooks/kosmos_postgresql/resources/server.rb

@@ -44,13 +44,14 @@ action :create do
 
   shared_buffers = if node['memory']['total'].to_i / 1024 < 1024 # < 1GB RAM
                      "128MB"
-                   else # >= 1GB RAM, use 50% of total RAM
-                     "#{node['memory']['total'].to_i / 1024 / 2}MB"
+                   else # >= 1GB RAM, use 25% of total RAM
+                     "#{node['memory']['total'].to_i / 1024 / 4}MB"
                    end
 
   additional_config = {
     max_connections: 200, # default
     shared_buffers: shared_buffers,
+    work_mem: "4MB",
     unix_socket_directories: "/var/run/postgresql",
     dynamic_shared_memory_type: "posix",
     timezone: "UTC", # default is GMT