Optimm to get all artists of a track in a single query

src/libs/database/impl/TrackArtistLink.cpp

@@ -39,19 +39,17 @@ namespace lms::db
             if (params.linkType)
                 query.where("t_a_l.type = ?").bind(*params.linkType);
 
-            if (params.track.isValid() || params.release.isValid())
+            if (params.track.isValid())
-                query.join("track t ON t.id = t_a_l.track_id");
+                query.where("t_a_l.track_id = ?").bind(params.track);
 
             if (params.artist.isValid())
-                query.join("artist a ON a.id = t_a_l.artist_id");
+                query.where("t_a_l.artist_id = ?").bind(params.artist);
 
             if (params.release.isValid())
+            {
+                query.join("track t ON t.id = t_a_l.track_id");
                 query.where("t.release_id = ?").bind(params.release);
-
+            }
-            if (params.track.isValid())
-                query.where("t.id = ?").bind(params.track);
-
-            query.groupBy("t_a_l.id");
 
             return query;
         }
@@ -81,6 +79,22 @@ namespace lms::db
         return utils::fetchQuerySingleResult(session.getDboSession()->find<TrackArtistLink>().where("id = ?").bind(id));
     }
 
+    void TrackArtistLink::find(Session& session, TrackId trackId, const std::function<void(const TrackArtistLink::pointer& link, const ObjectPtr<Artist>& artist)>& func)
+    {
+        session.checkReadTransaction();
+
+        using ResultType = std::tuple < Wt::Dbo::ptr<TrackArtistLink>, Wt::Dbo::ptr<Artist>>;
+
+        const auto query{ session.getDboSession()->query<ResultType>("SELECT t_a_l, a FROM track_artist_link t_a_l")
+        .join("artist a ON t_a_l.artist_id = a.id")
+        .where("t_a_l.track_id = ?").bind(trackId) };
+
+        utils::forEachQueryResult(query, [&](const ResultType& result)
+            {
+                func(std::get<Wt::Dbo::ptr<TrackArtistLink>>(result), std::get<Wt::Dbo::ptr<Artist>>(result));
+            });
+    }
+
     void TrackArtistLink::find(Session& session, const FindParameters& parameters, const std::function<void(const TrackArtistLink::pointer&)>& func)
     {
         const auto query{ createQuery(session, parameters) };

src/libs/database/include/database/TrackArtistLink.hpp

@@ -62,6 +62,7 @@ namespace lms::db
         TrackArtistLink() = default;
         TrackArtistLink(ObjectPtr<Track> track, ObjectPtr<Artist> artist, TrackArtistLinkType type, std::string_view subType);
 
+        static void                             find(Session& session, TrackId trackId, const std::function<void(const TrackArtistLink::pointer&, const ObjectPtr<Artist>&)>&);
         static void                             find(Session& session, const FindParameters& parameters, const std::function<void(const TrackArtistLink::pointer&)>&);
         static pointer 							find(Session& session, TrackArtistLinkId linkId);
         static pointer							create(Session& session, ObjectPtr<Track> track, ObjectPtr<Artist> artist, TrackArtistLinkType type, std::string_view subType = {});

src/libs/database/test/Artist.cpp

@@ -394,6 +394,29 @@ namespace lms::db::tests
             EXPECT_TRUE(types.contains(TrackArtistLinkType::Writer));
             EXPECT_FALSE(types.contains(TrackArtistLinkType::Composer));
         }
+
+        {
+            auto transaction{ session.createReadTransaction() };
+
+            std::vector<TrackArtistLink::pointer> visitedLinks;
+            TrackArtistLink::find(session, TrackArtistLink::FindParameters{}.setTrack(track.getId()), [&](const TrackArtistLink::pointer& link)
+                {
+                    visitedLinks.push_back(link);
+                });
+            ASSERT_EQ(visitedLinks.size(), 3);
+            EXPECT_EQ(visitedLinks[0]->getArtist()->getId(), artist.getId());
+            EXPECT_EQ(visitedLinks[1]->getArtist()->getId(), artist.getId());
+            EXPECT_EQ(visitedLinks[2]->getArtist()->getId(), artist.getId());
+
+            auto containsType = [&](TrackArtistLinkType type)
+                {
+                    return std::any_of(std::cbegin(visitedLinks), std::cend(visitedLinks), [type](const TrackArtistLink::pointer& link) { return link->getType() == type;});
+                };
+
+            EXPECT_TRUE(containsType(TrackArtistLinkType::Artist));
+            EXPECT_TRUE(containsType(TrackArtistLinkType::ReleaseArtist));
+            EXPECT_TRUE(containsType(TrackArtistLinkType::Writer));
+        }
     }
 
     TEST_F(DatabaseFixture, Artist_singleTrackMultiArtists)
@@ -453,6 +476,47 @@ namespace lms::db::tests
             tracks = Track::findIds(session, Track::FindParameters{}.setArtist(artist2->getId(), { TrackArtistLinkType::Artist }));
             EXPECT_EQ(tracks.results.size(), 1);
         }
+
+        {
+            auto transaction{ session.createReadTransaction() };
+
+            std::vector<TrackArtistLink::pointer> visitedLinks;
+            TrackArtistLink::find(session, TrackArtistLink::FindParameters{}.setTrack(track.getId()), [&](const TrackArtistLink::pointer& link)
+                {
+                    visitedLinks.push_back(link);
+                });
+            ASSERT_EQ(visitedLinks.size(), 2);
+            EXPECT_EQ(visitedLinks[0]->getArtist()->getId(), artist1.getId());
+            EXPECT_EQ(visitedLinks[1]->getArtist()->getId(), artist2.getId());
+        }
+
+        {
+            auto transaction{ session.createReadTransaction() };
+
+            std::vector<TrackArtistLink::pointer> visitedLinks;
+            TrackArtistLink::find(session, TrackArtistLink::FindParameters{}.setArtist(artist2.getId()), [&](const TrackArtistLink::pointer& link)
+                {
+                    visitedLinks.push_back(link);
+                });
+            ASSERT_EQ(visitedLinks.size(), 1);
+            EXPECT_EQ(visitedLinks[0]->getArtist()->getId(), artist2.getId());
+            EXPECT_EQ(visitedLinks[0]->getTrack()->getId(), track.getId());
+        }
+
+        {
+            auto transaction{ session.createReadTransaction() };
+
+            std::vector<std::pair<TrackArtistLink::pointer, Artist::pointer>> visitedEntries;
+            TrackArtistLink::find(session, track.getId(), [&](const TrackArtistLink::pointer& link, const Artist::pointer& artist)
+                {
+                    visitedEntries.push_back(std::make_pair(link, artist));
+                });
+            ASSERT_EQ(visitedEntries.size(), 2);
+            EXPECT_EQ(visitedEntries[0].first->getArtist()->getId(), artist1.getId());
+            EXPECT_EQ(visitedEntries[0].second->getId(), artist1.getId());
+            EXPECT_EQ(visitedEntries[1].first->getArtist()->getId(), artist2.getId());
+            EXPECT_EQ(visitedEntries[1].second->getId(), artist2.getId());
+        }
     }
 
     TEST_F(DatabaseFixture, Artist_findByName)

src/libs/subsonic/impl/responses/Contributor.cpp

@@ -26,14 +26,14 @@
 
 namespace lms::api::subsonic
 {
-    Response::Node createContributorNode(const db::ObjectPtr<db::TrackArtistLink>& trackArtistLink)
+    Response::Node createContributorNode(const db::ObjectPtr<db::TrackArtistLink>& trackArtistLink, const db::ObjectPtr<db::Artist>& artist)
     {
         Response::Node contributorNode;
 
         contributorNode.setAttribute("role", utils::toString(trackArtistLink->getType()));
         if (!trackArtistLink->getSubType().empty())
             contributorNode.setAttribute("subRole", trackArtistLink->getSubType());
-        contributorNode.addChild("artist", createArtistNode(trackArtistLink->getArtist()));
+        contributorNode.addChild("artist", createArtistNode(artist));
 
         return contributorNode;
     }

src/libs/subsonic/impl/responses/Contributor.hpp

@@ -24,10 +24,11 @@
 
 namespace lms::db
 {
+    class Artist;
     class TrackArtistLink;
 }
 
 namespace lms::api::subsonic
 {
-    Response::Node createContributorNode(const db::ObjectPtr<db::TrackArtistLink>& trackArtistLink);
+    Response::Node createContributorNode(const db::ObjectPtr<db::TrackArtistLink>& trackArtistLink, const db::ObjectPtr<db::Artist>& artist);
 }

src/libs/subsonic/impl/responses/Song.cpp

@@ -156,25 +156,22 @@ namespace lms::api::subsonic
         }
 
         {
-            TrackArtistLink::FindParameters params;
-            params.setTrack(track->getId());
-
             trackResponse.createEmptyArrayChild("albumartists");
             trackResponse.createEmptyArrayChild("artists");
             trackResponse.createEmptyArrayChild("contributors");
 
-            TrackArtistLink::find(context.dbSession, params, [&](const TrackArtistLink::pointer& link)
+            TrackArtistLink::find(context.dbSession, track->getId(), [&](const TrackArtistLink::pointer& link, const Artist::pointer& artist)
             {
                 switch (link->getType())
                 {
                     case TrackArtistLinkType::Artist:
-                        trackResponse.addArrayChild("artists", createArtistNode(link->getArtist()));
+                        trackResponse.addArrayChild("artists", createArtistNode(artist));
                         break;
                     case TrackArtistLinkType::ReleaseArtist:
-                        trackResponse.addArrayChild("albumartists", createArtistNode(link->getArtist()));
+                        trackResponse.addArrayChild("albumartists", createArtistNode(artist));
                         break;
                     default:
-                        trackResponse.addArrayChild("contributors", createContributorNode(link));
+                        trackResponse.addArrayChild("contributors", createContributorNode(link, artist));
                 }
             });
         }