Share one context per file store for performance reasons

There is now a CreateContext method for retrieving a stand-alone context for threaded use.

We may want to add safety against this context being disposed (or just return a fresh one if it is).

osu.Game/Database/DatabaseBackedStore.cs

@@ -11,12 +11,24 @@ namespace osu.Game.Database
     {
         protected readonly Storage Storage;
 
-        protected readonly Func<OsuDbContext> GetContext;
+        /// <summary>
+        /// Create a new <see cref="OsuDbContext"/> instance (separate from the shared context via <see cref="GetContext"/> for performing isolated operations.
+        /// </summary>
+        protected readonly Func<OsuDbContext> CreateContext;
 
-        protected DatabaseBackedStore(Func<OsuDbContext> getContext, Storage storage = null)
+        private readonly Lazy<OsuDbContext> queryContext;
+
+        /// <summary>
+        /// Retrieve a shared context for performing lookups (or write operations on the update thread, for now).
+        /// </summary>
+        protected OsuDbContext GetContext() => queryContext.Value;
+
+        protected DatabaseBackedStore(Func<OsuDbContext> createContext, Storage storage = null)
         {
+            CreateContext = createContext;
+            queryContext = new Lazy<OsuDbContext>(CreateContext);
+
             Storage = storage;
-            GetContext = getContext;
 
             try
             {

osu.Game/Database/OsuDbContext.cs

@@ -24,6 +24,7 @@ namespace osu.Game.Database
         public DbSet<DatabasedKeyBinding> DatabasedKeyBinding { get; set; }
         public DbSet<FileInfo> FileInfo { get; set; }
         public DbSet<RulesetInfo> RulesetInfo { get; set; }
+
         private readonly string connectionString;
 
         private static readonly Lazy<OsuDbLoggerFactory> logger = new Lazy<OsuDbLoggerFactory>(() => new OsuDbLoggerFactory());

osu.Game/IO/FileStore.cs

@@ -22,7 +22,7 @@ namespace osu.Game.IO
 
         public Storage Storage => base.Storage;
 
-        public FileStore(Func<OsuDbContext> getContext, Storage storage) : base(getContext, storage.GetStorageForDirectory(@"files"))
+        public FileStore(Func<OsuDbContext> createContext, Storage storage) : base(createContext, storage.GetStorageForDirectory(@"files"))
         {
             Store = new StorageBackedResourceStore(Storage);
         }

osu.Game/Input/KeyBindingStore.cs

@@ -17,8 +17,8 @@ namespace osu.Game.Input
     {
         public event Action KeyBindingChanged;
 
-        public KeyBindingStore(Func<OsuDbContext> getContext, RulesetStore rulesets, Storage storage = null)
+        public KeyBindingStore(Func<OsuDbContext> createContext, RulesetStore rulesets, Storage storage = null)
-            : base(getContext, storage)
+            : base(createContext, storage)
         {
             foreach (var info in rulesets.AvailableRulesets)
             {
@@ -38,13 +38,14 @@ namespace osu.Game.Input
 
         private void insertDefaults(IEnumerable<KeyBinding> defaults, int? rulesetId = null, int? variant = null)
         {
-            using (var context = GetContext())
+            var context = GetContext();
+
             using (var transaction = context.BeginTransaction())
             {
                 // compare counts in database vs defaults
                 foreach (var group in defaults.GroupBy(k => k.Action))
                 {
-                    int count = query(context, rulesetId, variant).Count(k => (int)k.Action == (int)group.Key);
+                    int count = Query(rulesetId, variant).Count(k => (int)k.Action == (int)group.Key);
                     int aimCount = group.Count();
 
                     if (aimCount <= count)
@@ -71,10 +72,8 @@ namespace osu.Game.Input
         /// <param name="rulesetId">The ruleset's internal ID.</param>
         /// <param name="variant">An optional variant.</param>
         /// <returns></returns>
-        public IEnumerable<KeyBinding> Query(int? rulesetId = null, int? variant = null) => query(GetContext(), rulesetId, variant);
+        public IEnumerable<KeyBinding> Query(int? rulesetId = null, int? variant = null) =>
-
+            GetContext().DatabasedKeyBinding.Where(b => b.RulesetID == rulesetId && b.Variant == variant);
-        private IEnumerable<KeyBinding> query(OsuDbContext context, int? rulesetId = null, int? variant = null) =>
-            context.DatabasedKeyBinding.Where(b => b.RulesetID == rulesetId && b.Variant == variant);
 
         public void Update(KeyBinding keyBinding)
         {

osu.Game/Overlays/Settings/Sections/Maintenance/GeneralSettings.cs

@@ -1,6 +1,7 @@
 // Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
 // Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
 
+using System.Linq;
 using System.Threading.Tasks;
 using osu.Framework.Allocation;
 using osu.Framework.Graphics;
@@ -51,7 +52,7 @@ namespace osu.Game.Overlays.Settings.Sections.Maintenance
                         restoreButton.Enabled.Value = false;
                         Task.Run(() =>
                         {
-                            foreach (var b in beatmaps.QueryBeatmaps(b => b.Hidden))
+                            foreach (var b in beatmaps.QueryBeatmaps(b => b.Hidden).ToList())
                                 beatmaps.Restore(b);
                         }).ContinueWith(t => Schedule(() => restoreButton.Enabled.Value = true));
                     }