Fixed: Cleanup unused Tags during housekeeping.

src/NzbDrone.Core.Test/Housekeeping/Housekeepers/CleanupUnusedTagsFixture.cs

@@ -0,0 +1,43 @@
+using FizzWare.NBuilder;
+using FluentAssertions;
+using NUnit.Framework;
+using NzbDrone.Core.Download.Pending;
+using NzbDrone.Core.Housekeeping.Housekeepers;
+using NzbDrone.Core.Parser.Model;
+using NzbDrone.Core.Test.Framework;
+using NzbDrone.Core.Tv;
+using NzbDrone.Core.Tags;
+using NzbDrone.Core.Restrictions;
+
+namespace NzbDrone.Core.Test.Housekeeping.Housekeepers
+{
+    [TestFixture]
+    public class CleanupUnusedTagsFixture : DbTest<CleanupUnusedTags, Tag>
+    {
+        [Test]
+        public void should_delete_unused_tags()
+        {
+            var tags = Builder<Tag>.CreateListOfSize(2).BuildList();
+
+            Db.InsertMany(tags);
+            Subject.Clean();
+            AllStoredModels.Should().BeEmpty();
+        }
+
+        [Test]
+        public void should_not_delete_used_tags()
+        {
+            var tags = Builder<Tag>.CreateListOfSize(2).BuildList();
+            Db.InsertMany(tags);
+
+            var restrictions = Builder<Restriction>.CreateListOfSize(2)
+                .All()
+                .With(v => v.Tags.Add(tags[0].Id))
+                .BuildList();
+            Db.InsertMany(restrictions);
+
+            Subject.Clean();
+            AllStoredModels.Should().HaveCount(1);
+        }
+    }
+}

src/NzbDrone.Core.Test/NzbDrone.Core.Test.csproj

@@ -224,6 +224,7 @@
     <Compile Include="Housekeeping\Housekeepers\CleanupOrphanedIndexerStatusFixture.cs" />
     <Compile Include="Housekeeping\Housekeepers\CleanupOrphanedHistoryItemsFixture.cs" />
     <Compile Include="Housekeeping\Housekeepers\CleanupOrphanedMetadataFilesFixture.cs" />
+    <Compile Include="Housekeeping\Housekeepers\CleanupUnusedTagsFixture.cs" />
     <Compile Include="Housekeeping\Housekeepers\CleanupOrphanedPendingReleasesFixture.cs" />
     <Compile Include="Housekeeping\Housekeepers\FixFutureRunScheduledTasksFixture.cs" />
     <Compile Include="Http\HttpProxySettingsProviderFixture.cs" />

src/NzbDrone.Core/Housekeeping/Housekeepers/CleanupUnusedTags.cs

@@ -0,0 +1,41 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Marr.Data;
+using NzbDrone.Common.Serializer;
+using NzbDrone.Core.Datastore;
+
+namespace NzbDrone.Core.Housekeeping.Housekeepers
+{
+    public class CleanupUnusedTags : IHousekeepingTask
+    {
+        private readonly IMainDatabase _database;
+
+        public CleanupUnusedTags(IMainDatabase database)
+        {
+            _database = database;
+        }
+
+        public void Clean()
+        {
+            var mapper = _database.GetDataMapper();
+
+            var usedTags = new[] { "Series", "Notifications", "DelayProfiles", "Restrictions" }
+                .SelectMany(v => GetUsedTags(v, mapper))
+                .Distinct()
+                .ToArray();
+
+            var usedTagsList = string.Join(",", usedTags.Select(d => d.ToString()).ToArray());
+
+            mapper.ExecuteNonQuery($"DELETE FROM Tags WHERE NOT Id IN ({usedTagsList})");
+        }
+
+        private int[] GetUsedTags(string table, IDataMapper mapper)
+        {
+            return mapper.ExecuteReader($"SELECT DISTINCT Tags FROM {table} WHERE NOT Tags = '[]'", reader => reader.GetString(0))
+                         .SelectMany(Json.Deserialize<List<int>>)
+                         .Distinct()
+                         .ToArray();
+        }
+    }
+}

src/NzbDrone.Core/NzbDrone.Core.csproj

@@ -545,6 +545,7 @@
     <Compile Include="Housekeeping\Housekeepers\CleanupOrphanedIndexerStatus.cs" />
     <Compile Include="Housekeeping\Housekeepers\CleanupOrphanedHistoryItems.cs" />
     <Compile Include="Housekeeping\Housekeepers\CleanupOrphanedMetadataFiles.cs" />
+    <Compile Include="Housekeeping\Housekeepers\CleanupUnusedTags.cs" />
     <Compile Include="Housekeeping\Housekeepers\CleanupOrphanedPendingReleases.cs" />
     <Compile Include="Housekeeping\Housekeepers\DeleteBadMediaCovers.cs" />
     <Compile Include="Housekeeping\Housekeepers\FixFutureRunScheduledTasks.cs" />