feat: implement migration tracking and history management for PostgreSQL

MediaBrowser.Controller/Entities/Folder.cs

@@ -420,6 +420,7 @@ namespace MediaBrowser.Controller.Entities
 
                 // Create a list for our validated children
                 var newItems = new List<BaseItem>();
+                var changedItems = new List<BaseItem>();
 
                 cancellationToken.ThrowIfCancellationRequested();
 
@@ -436,7 +437,7 @@ namespace MediaBrowser.Controller.Entities
 
                         if (currentChild.UpdateFromResolvedItem(child) > ItemUpdateType.None)
                         {
-                            await currentChild.UpdateToRepositoryAsync(ItemUpdateType.MetadataImport, cancellationToken).ConfigureAwait(false);
+                            changedItems.Add(currentChild);
                         }
                         else
                         {
@@ -484,6 +485,11 @@ namespace MediaBrowser.Controller.Entities
                     LibraryManager.CreateItems(newItems, this, cancellationToken);
                 }
 
+                if (changedItems.Count > 0)
+                {
+                    await LibraryManager.UpdateItemsAsync(changedItems, this, ItemUpdateType.MetadataImport, cancellationToken).ConfigureAwait(false);
+                }
+
                 // After removing items, reattach any detached user data to remaining children
                 // that share the same user data keys (eg. same episode replaced with a new file).
                 if (actuallyRemoved.Count > 0)

MediaBrowser.Controller/LibraryTaskScheduler/LimitedConcurrencyLibraryScheduler.cs

@@ -115,7 +115,7 @@ public sealed class LimitedConcurrencyLibraryScheduler : ILimitedConcurrencyLibr
         if (fanoutConcurrency <= 0)
         {
             // in case the user did not set a limit manually, we can assume he has 3 or more cores as already checked by ShouldForceSequentialOperation.
-            return Environment.ProcessorCount - 3;
+            return Math.Max(2, Environment.ProcessorCount / 2);
         }
 
         return fanoutConcurrency;