[GitHub] [couchdb] nickva commented on a diff in pull request #4238: Optimize _bulk_get endpoint

[GitBox <gi...@apache.org>]

nickva commented on code in PR #4238:
URL: https://github.com/apache/couchdb/pull/4238#discussion_r1005148598


##########
src/chttpd/src/chttpd_db.erl:
##########
@@ -2363,6 +2288,175 @@ set_namespace(NS, #mrargs{} = Args) ->
 
 %% /db/_bulk_get stuff
 
+bulk_get_is_multipart(#httpd{mochi_req = MochiReq}) ->
+    Json = MochiReq:accepts_content_type("application/json"),
+    Mixed = MochiReq:accepts_content_type("multipart/mixed"),
+    Related = MochiReq:accepts_content_type("multipart/related"),
+    not Json andalso (Mixed orelse Related).
+
+bulk_get_docs(Db, #{} = ArgsMap, Options) ->
+    % Sort args by doc ID to hopefully make querying B-trees a bit faster
+    KeyFun = fun({Ref, {DocId, _, _}}) -> {DocId, Ref} end,
+    CmpFun = fun(A, B) -> KeyFun(A) =< KeyFun(B) end,
+    ArgsList = lists:sort(CmpFun, maps:to_list(ArgsMap)),
+    % Split out known errors. Later, before returning, recombine them back into
+    % the final result map.
+    PartFun = fun({_Ref, {_DocId, RevsOrError, _DocOpts}}) ->
+        case RevsOrError of
+            L when is_list(L) -> true;
+            all -> true;
+            {error, _} -> false
+        end
+    end,
+    {ValidArgs, ErrorArgs} = lists:partition(PartFun, ArgsList),
+    UseBatches = config:get_boolean("chttpd", "bulk_get_use_batches", true),
+    Responses =
+        case UseBatches of
+            true -> bulk_get_docs_batched(Db, ValidArgs, Options);
+            false -> bulk_get_docs_individually(Db, ValidArgs, Options)
+        end,
+    MapFun = fun({Ref, {DocId, Response, _}} = RespTuple) ->
+        case Response of
+            [] ->
+                % Remap empty reponses to errors. This is a peculiarity of the
+                % _bulk_get HTTP API. If revision was not specifed, `undefined`
+                % must be returned as the error revision ID.
+                #{Ref := {_, Revs, _}} = ArgsMap,
+                RevStr = bulk_get_rev_error(Revs),
+                Error = {RevStr, <<"not_found">>, <<"missing">>},
+                {Ref, {DocId, {error, Error}, []}};
+            [_ | _] = DocRevisions ->

Review Comment:
   [Yup](https://medium.com/erlang-battleground/ode-to-the-robot-butt-bbd69e69beb2)!



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