Erlang - Global Variables .. yes I know, I know

Question

Ok I have been trying every which way to figure this out.

I need to get this table to be a global.. I have realized it is much less efficient to pass TableID around.. in the scope of my program.

So I tried creating a new table then looking it up:

TableID = ets:new(tb, [set,public]),
put({tableUniqueID}, TableID),

Then I used:

get({tableUniqueID})

And in the same function it returns TableID just fine... yet when I use it in another function, it returns an undefined.

What?? I thought get and put made a key global..

ALSO before all this I realized you "could" call a table lookup function as such:

ets:lookup(get({tableUniqueID}), msgIn)

Same thing, in function works, outside does not.. Get Put problem..

Then I realized another way to Lookup a table would be by calling the atom of the table

ets:lookup(tb, msgIn)

But this NEVER works, not inside the function, not out..

So my main priority would be to figure why looking up a table by its atom, is not possible. But it says it is most everywhere, including the manual.

The get/put I could live without, As long as I can store table, then lookup the table by its atom identifier.

Can anyone shed light on this dilemma.

Thanks, -B

Answer 1

I GOT IT!!

Wish the docs, would say this under the lookup function.. Better yet, everyone who writes tutorials on ets, or more so books

The solution is to

TableID = ets:new(tb, [set,public,named_table])

That named_table is the important part

Some digging through man pages, but

;)

Answer 2

The correct answer to your problem is to not use a global table at all, but to rather pass around the information. Especially since you mention efficiency in your original question. You are creating a congestion point in your code which will make it have worse performance on any multi core machine.

The ets table is implemented as a process that all other processes have to call to get a value.