[erlang-questions] Key-value stores and value part

Max Bourinov <>
Sat Feb 25 17:21:11 CET 2012


You can try something like this:

Key = term(),
Value =[{Key :: atom(), Value :: term()]

With this approach you can dynamically manage fields in your Value. Of
course some extra business logic and helper functions are needed.



Sent from my iPhone

On 25.02.2012, at 6:37, Vinayak Pawar <> wrote:

Hi,

I've a key-value store. The value part is a tuple stored using
term_to_binary().

    -record(some_rec, {e1, e2}).

    Rec = #some_rec{e1 = E1, e2 = E2}
    kv_store:put(Key, term_to_binary(Rec)).

I access the values in this key-value store as below:

    case kv_store:get(Key) of
        {ok, Bin} ->
            #some_rec{} = Rec = binary_to_term(Bin),
            do_some_work(Rec);

        false ->
            do_something_else(Key)
    end.

Now there is change in my tuple structure. A new element/field is been
added to it:

    -record(some_rec, {e1, e2, e3}).

Henceforth tuples with this new structure will get stored in the KV store.

This means, everytime I change the tuple structure, I need to run through
each key-value pair that has been stored using older tuple structure and
update the value part to be in sync with new tuple structure?

This gives a hint that I'm doing something wrong in the way I store the
values in schema-less KV store. Can you please help me figure out what is
wrong?

Question: is it possible to store values in KV store so that I don't have
to update the KV store whenever there is change in tuple structure? store
values in JSON form?

Regards,
Vinayak

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