On Mon, Aug 10, 2009 at 8:01 AM, Norman Barker<[email protected]> wrote:
> Hi,
>
> I commented on this in a recent thread, a couple of minutes later I
> had a working example (compliments to the modular design of couchdb
> and the easy set up with an ini file).
>
> Folloing Joe Armstrong's book on pmap I have
>
> update_db(JsonObject, Db)->
> NewDoc = couch_doc:from_json_obj(JsonObject),
> DocId = couch_util:new_uuid(),
> {ok, _NewRev} = couch_db:update_doc(Db, NewDoc#doc{id=DocId}, []).
>
You should just change this function to accept a list of docs.
couch_db:update_docs takes a list.
Writing a batch of docs in serial is much faster than doing it in
parallel would be (if you could even get it to work).
>
> pmap(F, L, Db) ->
> S = self(),
> %% make_ref() returns a unique reference
> %% we'll match on this later
> Ref = erlang:make_ref(),
> Pids = map(fun(I) ->
> spawn(fun() -> do_f(S, Ref, F, I, Db) end)
> end, L),
> %% gather the results
> gather(Pids, Ref).
>
> do_f(Parent, Ref, F, I, Db) ->
> Parent ! {self(), Ref, (catch F(I, Db))}.
>
> gather([Pid|T], Ref) ->
> receive
> {Pid, Ref, Ret} -> [Ret|gather(T, Ref)]
> end;
>
> gather([], _) ->
> [].
>
>
> and then I invoke this with
>
> {FormResp} = my_update_query_servers:render_update(Lang, UpFun,
> nil, nil, Req, Db),
> case proplists:get_value(<<"results">>, FormResp, nil) of
> undefined ->
> throw({error, no_result});
> ResultList ->
> Res = pmap(fun update_db/2, ResultList, Db)
> end,
>
>
> is there something bad with this? my_update_query_servers returns a
> collection of JSON objects and this seems to me to be a parallel
> write. Since I gather all the references I should be able to update
> the caller with the list of created documents?
>
> Norman
>
--
Chris Anderson
http://jchrisa.net
http://couch.io
