Faster tag view in UI for large libraries

(cherry picked from commit b050e1d2eb3bff9e28e7a1545d121be091789308)

Closes #3762

src/NzbDrone.Core/Music/Repositories/ArtistRepository.cs

@@ -13,6 +13,7 @@ namespace NzbDrone.Core.Music
         Artist FindByName(string cleanName);
         Artist FindById(string foreignArtistId);
         Dictionary<int, string> AllArtistPaths();
+        Dictionary<int, List<int>> AllArtistsTags();
         Artist GetArtistByMetadataId(int artistMetadataId);
         List<Artist> GetArtistByMetadataId(IEnumerable<int> artistMetadataId);
     }
@@ -79,6 +80,15 @@ namespace NzbDrone.Core.Music
             }
         }
 
+        public Dictionary<int, List<int>> AllArtistsTags()
+        {
+            using (var conn = _database.OpenConnection())
+            {
+                var strSql = "SELECT \"Id\" AS \"Key\", \"Tags\" AS \"Value\" FROM \"Artists\" WHERE \"Tags\" IS NOT NULL";
+                return conn.Query<KeyValuePair<int, List<int>>>(strSql).ToDictionary(x => x.Key, x => x.Value);
+            }
+        }
+
         public List<Artist> GetArtistByMetadataId(IEnumerable<int> artistMetadataIds)
         {
             return Query(s => artistMetadataIds.Contains(s.ArtistMetadataId));

src/NzbDrone.Core/Music/Services/ArtistService.cs

@@ -24,6 +24,7 @@ namespace NzbDrone.Core.Music
         void DeleteArtist(int artistId, bool deleteFiles, bool addImportListExclusion = false);
         void DeleteArtists(List<int> artistIds, bool deleteFiles, bool addImportListExclusion = false);
         List<Artist> GetAllArtists();
+        Dictionary<int, List<int>> GetAllArtistsTags();
         List<Artist> AllForTag(int tagId);
         Artist UpdateArtist(Artist artist, bool publishUpdatedEvent = true);
         List<Artist> UpdateArtists(List<Artist> artist, bool useExistingRelativeFolder);
@@ -189,6 +190,11 @@ namespace NzbDrone.Core.Music
             return _artistRepository.AllArtistPaths();
         }
 
+        public Dictionary<int, List<int>> GetAllArtistsTags()
+        {
+            return _artistRepository.AllArtistsTags();
+        }
+
         public List<Artist> AllForTag(int tagId)
         {
             return GetAllArtists().Where(s => s.Tags.Contains(tagId))

src/NzbDrone.Core/Tags/TagService.cs

@@ -106,7 +106,7 @@ namespace NzbDrone.Core.Tags
             var importLists = _importListFactory.All();
             var notifications = _notificationFactory.All();
             var restrictions = _releaseProfileService.All();
-            var artists = _artistService.GetAllArtists();
+            var artists = _artistService.GetAllArtistsTags();
             var rootFolders = _rootFolderService.All();
             var indexers = _indexerService.All();
 
@@ -122,7 +122,7 @@ namespace NzbDrone.Core.Tags
                     ImportListIds = importLists.Where(c => c.Tags.Contains(tag.Id)).Select(c => c.Id).ToList(),
                     NotificationIds = notifications.Where(c => c.Tags.Contains(tag.Id)).Select(c => c.Id).ToList(),
                     RestrictionIds = restrictions.Where(c => c.Tags.Contains(tag.Id)).Select(c => c.Id).ToList(),
-                    ArtistIds = artists.Where(c => c.Tags.Contains(tag.Id)).Select(c => c.Id).ToList(),
+                    ArtistIds = artists.Where(c => c.Value.Contains(tag.Id)).Select(c => c.Key).ToList(),
                     RootFolderIds = rootFolders.Where(c => c.DefaultTags.Contains(tag.Id)).Select(c => c.Id).ToList(),
                     IndexerIds = indexers.Where(c => c.Tags.Contains(tag.Id)).Select(c => c.Id).ToList()
                 });