Checking session subtable in IRule

I don't think it is possible to distinguish, why would you need to do that? I believe a subtable with all keys removed simply ceases to exist...

if {[table keys -subtable sometable -count] ==0} { subtable is empty or does not exist }

if you really need to do this then you can place a dummy key in your subtable and ccheck for it using "-mustexist" option.

Extract from Wiki: https://devcentral.f5.com/wiki/iRules.table.ashx?lc=1

" If -mustexist is specified, and the key does not already exist, no action will be taken, and an empty string will be returned. Cannot be specified with -excl.If -excl is specified, and the key already exists, the key will not be inserted, and the existing value will be returned. Cannot be specified with -mustexist. "

Hope this helps,

Sam