Emit Tuples From Erlang Views In CouchDB

Question

CouchDB, version 0.10.0, using native erlang views.

I have a simple document of the form:

{
   \"_id\": \"user-1\",
   \"_rev\": \"1-9ccf63b66b62d15d         


        

Answer 1

The JSON object {"foo":"bar","baz":1} is {[{<<"foo">>,<<"bar">>},{<<"baz">>,1}]}

In Erlang lingua it is a proplist wrapped in a tuple.

It's not pretty, but very efficient :)

To get a feel for it you can play with the JSON lib that ships with CouchDB:

1. Start CouchDB with the -i (interactive) flag
2. On the resulting erlang shell, type: couch_util:json_decode(<<"{\"foo\":\"bar\"}">>).
3. Profit

// in later versions of CouchDB, this is ejson:decode()

Answer 2

If you like experimental features (that still work...), you might want to have a look to Erlang exprecs.

I found it extremely helpful in creating a sort of dynamic records for Erlang.

Answer 3

For test_suite_reports bd, that has tests field:

[
   {
       "name": "basics",
       "status": "success",
       "duration": 21795
   },
   {
       "name": "all_docs",
       "status": "success",
       "duration": 385
   } ...

I have wrote this to get name and status:

fun({Doc}) ->
  Name = fun(L) ->  proplists:get_value(<<"name">>, L, null) end,
  Status = fun(L) -> proplists:get_value(<<"status">>, L, null) end,
  Tests = proplists:get_value(<<"tests">>, Doc, null),
  lists:foreach(fun({L}) -> Emit(Name(L), Status(L)) end, Tests)
end.