Implement fabric2_db:get_design_docs/1prototype/fdb-layer-get-design-docs

This is a more efficient method to get all of the design documents than
relying on fabric2_db:fold_docs which doesn't load doc bodies in
parallel.

1 files changed, 25 insertions, 3 deletions

diff --git a/src/fabric/src/fabric2_db.erl b/src/fabric/src/fabric2_db.erl
index 129dea2d7..0f0ed8f41 100644
--- a/src/fabric/src/fabric2_db.erl
+++ b/src/fabric/src/fabric2_db.erl
@@ -80,9 +80,7 @@
     get_full_doc_info/2,
     get_full_doc_infos/2,
     get_missing_revs/2,
-    %% get_design_doc/2,
-    %% get_design_docs/1,
-    %% get_design_doc_count/1,
+    get_design_docs/1,
     %% get_purge_infos/2,
 
     %% get_minimum_purge_seq/1,
@@ -657,6 +655,30 @@ get_missing_revs(Db, JsonIdRevs) ->
     {ok, AllMissing}.
 
 
+get_design_docs(Db) ->
+    fabric2_fdb:transactional(Db, fun(TxDb) ->
+        #{
+            db_prefix := DbPrefix
+        } = TxDb,
+
+        Prefix = erlfdb_tuple:pack({?DB_CHANGES}, DbPrefix),
+        Opts = set_design_doc_keys([]),
+        Fun = fun({Key, Val}, Acc) ->
+            {DocId} = erlfdb_tuple:unpack(K, Prefix),
+            RevId = erlfdb_tuple:unpack(V),
+            Future = get_doc_body_future(TxDb, DocId, RevId),
+            [Future | Acc]
+        end,
+        {ok, Futures} = fabric2_fdb:fold_range(TxDb, Prefix, Fun, [], Opts),
+
+        % Using foldl instead of map means that the design
+        % docs come out in sorted order.
+        lists:foldl(fun(Future, Acc) ->
+            [fabric2_fdb:get_doc_body_wait(Future) | Acc]
+        end, [], Futures)
+    end).
+
+
 validate_docid(<<"">>) ->
     throw({illegal_docid, <<"Document id must not be empty">>});
 validate_docid(<<"_design/">>) ->