Count distinct items for byName ItemCounts and batch every kind

8 files changed, 1185 insertions, 261 deletions

diff --git a/Emby.Server.Implementations/Dto/DtoService.cs b/Emby.Server.Implementations/Dto/DtoService.cs
index a2d3e14439..59e75691dc 100644
--- a/Emby.Server.Implementations/Dto/DtoService.cs
+++ b/Emby.Server.Implementations/Dto/DtoService.cs
@@ -185,6 +185,13 @@ namespace Emby.Server.Implementations.Dto
                 allCollectionFolders = _libraryManager.GetUserRootFolder().Children.OfType<Folder>().ToList();
             }
 
+            // Batch-fetch by-name item counts to avoid N+1 queries
+            Dictionary<Guid, ItemCounts>? itemCountsBatch = null;
+            if (options.ContainsField(ItemFields.ItemCounts))
+            {
+                itemCountsBatch = GetItemCountsBatch(accessibleItems, user);
+            }
+
             // Batch-fetch child counts for all folders to avoid N+1 queries
             Dictionary<Guid, int>? childCountBatch = null;
             if (options.ContainsField(ItemFields.ChildCount))
@@ -293,7 +300,7 @@ namespace Emby.Server.Implementations.Dto
 
                 if (options.ContainsField(ItemFields.ItemCounts))
                 {
-                    SetItemByNameInfo(dto, user);
+                    SetItemByNameInfo(dto, user, itemCountsBatch);
                 }
 
                 returnItems[index] = dto;
@@ -518,14 +525,36 @@ namespace Emby.Server.Implementations.Dto
             return dto;
         }
 
-        private void SetItemByNameInfo(BaseItemDto dto, User? user)
+        private Dictionary<Guid, ItemCounts> GetItemCountsBatch(IReadOnlyList<BaseItem> items, User? user)
+        {
+            var result = new Dictionary<Guid, ItemCounts>();
+
+            foreach (var group in items.GroupBy(item => item.GetBaseItemKind()))
+            {
+                if (!_relatedItemKinds.TryGetValue(group.Key, out var relatedItemKinds))
+                {
+                    continue;
+                }
+
+                var ids = group.Select(item => item.Id).ToArray();
+                foreach (var (id, counts) in _libraryManager.GetItemCountsForNameItems(group.Key, ids, relatedItemKinds, user))
+                {
+                    result[id] = counts;
+                }
+            }
+
+            return result;
+        }
+
+        private void SetItemByNameInfo(BaseItemDto dto, User? user, IReadOnlyDictionary<Guid, ItemCounts>? prefetchedCounts = null)
         {
             if (!_relatedItemKinds.TryGetValue(dto.Type, out var relatedItemKinds))
             {
                 return;
             }
 
-            var counts = _libraryManager.GetItemCountsForNameItem(dto.Type, dto.Id, relatedItemKinds, user);
+            var counts = prefetchedCounts?.GetValueOrDefault(dto.Id)
+                ?? _libraryManager.GetItemCountsForNameItem(dto.Type, dto.Id, relatedItemKinds, user);
 
             dto.AlbumCount = counts.AlbumCount;
             dto.ArtistCount = counts.ArtistCount;
diff --git a/Jellyfin.Server.Implementations/Item/BaseItemRepository.ByName.cs b/Jellyfin.Server.Implementations/Item/BaseItemRepository.ByName.cs
index 70e4ca3b1d..cdc8744642 100644
--- a/Jellyfin.Server.Implementations/Item/BaseItemRepository.ByName.cs
+++ b/Jellyfin.Server.Implementations/Item/BaseItemRepository.ByName.cs
@@ -319,14 +319,7 @@ public sealed partial class BaseItemRepository
             .WhereOneOrMany(cleanNames, ivm => ivm.ItemValue.CleanValue);
 
         var seriesTypeName = _itemTypeLookup.BaseItemKindNames[BaseItemKind.Series];
-        var movieTypeName = _itemTypeLookup.BaseItemKindNames[BaseItemKind.Movie];
         var episodeTypeName = _itemTypeLookup.BaseItemKindNames[BaseItemKind.Episode];
-        var musicAlbumTypeName = _itemTypeLookup.BaseItemKindNames[BaseItemKind.MusicAlbum];
-        var musicArtistTypeName = _itemTypeLookup.BaseItemKindNames[BaseItemKind.MusicArtist];
-        var musicVideoTypeName = _itemTypeLookup.BaseItemKindNames[BaseItemKind.MusicVideo];
-        var programTypeName = _itemTypeLookup.BaseItemKindNames[BaseItemKind.LiveTvProgram];
-        var audioTypeName = _itemTypeLookup.BaseItemKindNames[BaseItemKind.Audio];
-        var trailerTypeName = _itemTypeLookup.BaseItemKindNames[BaseItemKind.Trailer];
 
         // Rewrite query to avoid SelectMany on navigation properties (which requires SQL APPLY, not supported on SQLite)
         // Instead, start from ItemValueMaps and join with BaseItems.
@@ -335,9 +328,9 @@ public sealed partial class BaseItemRepository
                 scopedItems,
                 ivm => ivm.ItemId,
                 e => e.Id,
-                (ivm, e) => new { CleanName = ivm.ItemValue.CleanValue, e.Type, e.SeriesId })
+                (ivm, e) => new { CleanName = ivm.ItemValue.CleanValue, e.Type, e.SeriesId, e.Id })
             .GroupBy(x => new { x.CleanName, x.Type, x.SeriesId })
-            .Select(g => new { g.Key.CleanName, g.Key.Type, g.Key.SeriesId, Count = g.Count() })
+            .Select(g => new { g.Key.CleanName, g.Key.Type, g.Key.SeriesId, Count = g.Select(x => x.Id).Distinct().Count() })
             .ToList();
 
         // Only studios and genres pass down from a series to its episodes; an artist credit does not.
@@ -359,46 +352,10 @@ public sealed partial class BaseItemRepository
 
         foreach (var group in rawCounts.GroupBy(x => x.CleanName))
         {
-            var counts = new ItemCounts();
-            foreach (var row in group)
-            {
-                if (row.Type == seriesTypeName)
-                {
-                    counts.SeriesCount += row.Count;
-                }
-                else if (row.Type == movieTypeName)
-                {
-                    counts.MovieCount += row.Count;
-                }
-                else if (row.Type == musicAlbumTypeName)
-                {
-                    counts.AlbumCount += row.Count;
-                }
-                else if (row.Type == musicArtistTypeName)
-                {
-                    counts.ArtistCount += row.Count;
-                }
-                else if (row.Type == musicVideoTypeName)
-                {
-                    counts.MusicVideoCount += row.Count;
-                }
-                else if (row.Type == programTypeName)
-                {
-                    counts.ProgramCount += row.Count;
-                }
-                else if (row.Type == audioTypeName)
-                {
-                    counts.SongCount += row.Count;
-                }
-                else if (row.Type == trailerTypeName)
-                {
-                    counts.TrailerCount += row.Count;
-                }
-            }
+            var counts = ItemCountBuilder.Build(_itemTypeLookup, group.Select(row => (row.Type, row.Count)));
 
             // Episodes are counted separately: the value is usually only written on the series.
-            counts.EpisodeCount = episodeCounts.GetValueOrDefault(group.Key);
-            counts.ItemCount = counts.TotalItemCount();
+            ItemCountBuilder.SetEpisodeCount(counts, episodeCounts.GetValueOrDefault(group.Key));
             countsByCleanName[group.Key] = counts;
         }
 
@@ -407,7 +364,9 @@ public sealed partial class BaseItemRepository
         {
             if (!countsByCleanName.ContainsKey(cleanName))
             {
-                countsByCleanName[cleanName] = new ItemCounts { EpisodeCount = episodeCount, ItemCount = episodeCount };
+                var counts = new ItemCounts();
+                ItemCountBuilder.SetEpisodeCount(counts, episodeCount);
+                countsByCleanName[cleanName] = counts;
             }
         }
 
diff --git a/Jellyfin.Server.Implementations/Item/ItemCountBuilder.cs b/Jellyfin.Server.Implementations/Item/ItemCountBuilder.cs
new file mode 100644
index 0000000000..0f8a1b9dfe
--- /dev/null
+++ b/Jellyfin.Server.Implementations/Item/ItemCountBuilder.cs
@@ -0,0 +1,96 @@
+using System;
+using System.Collections.Generic;
+using Jellyfin.Data.Enums;
+using MediaBrowser.Controller.Persistence;
+using MediaBrowser.Model.Dto;
+
+namespace Jellyfin.Server.Implementations.Item;
+
+/// <summary>
+/// Turns per-type counts into an <see cref="ItemCounts"/>.
+/// </summary>
+internal static class ItemCountBuilder
+{
+    /// <summary>
+    /// Builds the counts of one by-name item.
+    /// </summary>
+    /// <param name="itemTypeLookup">The item type lookup.</param>
+    /// <param name="counts">The counted items, by type name. A type may repeat.</param>
+    /// <returns>The counts.</returns>
+    public static ItemCounts Build(IItemTypeLookup itemTypeLookup, IEnumerable<(string Type, int Count)> counts)
+    {
+        ArgumentNullException.ThrowIfNull(itemTypeLookup);
+        ArgumentNullException.ThrowIfNull(counts);
+
+        var lookup = itemTypeLookup.BaseItemKindNames;
+        var result = new ItemCounts();
+
+        foreach (var (type, count) in counts)
+        {
+            // Accumulated rather than assigned: a caller may group by something finer than the
+            // type and hand the same type over more than once.
+            if (string.Equals(type, lookup[BaseItemKind.MusicAlbum], StringComparison.Ordinal))
+            {
+                result.AlbumCount += count;
+            }
+            else if (string.Equals(type, lookup[BaseItemKind.MusicArtist], StringComparison.Ordinal))
+            {
+                result.ArtistCount += count;
+            }
+            else if (string.Equals(type, lookup[BaseItemKind.Episode], StringComparison.Ordinal))
+            {
+                result.EpisodeCount += count;
+            }
+            else if (string.Equals(type, lookup[BaseItemKind.Movie], StringComparison.Ordinal))
+            {
+                result.MovieCount += count;
+            }
+            else if (string.Equals(type, lookup[BaseItemKind.MusicVideo], StringComparison.Ordinal))
+            {
+                result.MusicVideoCount += count;
+            }
+            else if (string.Equals(type, lookup[BaseItemKind.LiveTvProgram], StringComparison.Ordinal))
+            {
+                result.ProgramCount += count;
+            }
+            else if (string.Equals(type, lookup[BaseItemKind.Series], StringComparison.Ordinal))
+            {
+                result.SeriesCount += count;
+            }
+            else if (string.Equals(type, lookup[BaseItemKind.Audio], StringComparison.Ordinal))
+            {
+                result.SongCount += count;
+            }
+            else if (string.Equals(type, lookup[BaseItemKind.Trailer], StringComparison.Ordinal))
+            {
+                result.TrailerCount += count;
+            }
+            else if (string.Equals(type, lookup[BaseItemKind.BoxSet], StringComparison.Ordinal))
+            {
+                result.BoxSetCount += count;
+            }
+            else if (string.Equals(type, lookup[BaseItemKind.Book], StringComparison.Ordinal))
+            {
+                result.BookCount += count;
+            }
+        }
+
+        result.ItemCount = result.TotalItemCount();
+
+        return result;
+    }
+
+    /// <summary>
+    /// Replaces the episode count, which both by-name paths decide separately from the other
+    /// types because a genre or studio is usually written on the series rather than its episodes.
+    /// </summary>
+    /// <param name="counts">The counts to update.</param>
+    /// <param name="episodeCount">The episode count.</param>
+    public static void SetEpisodeCount(ItemCounts counts, int episodeCount)
+    {
+        ArgumentNullException.ThrowIfNull(counts);
+
+        counts.EpisodeCount = episodeCount;
+        counts.ItemCount = counts.TotalItemCount();
+    }
+}
diff --git a/Jellyfin.Server.Implementations/Item/ItemCountService.cs b/Jellyfin.Server.Implementations/Item/ItemCountService.cs
index 8b0aac2836..57705cdf11 100644
--- a/Jellyfin.Server.Implementations/Item/ItemCountService.cs
+++ b/Jellyfin.Server.Implementations/Item/ItemCountService.cs
@@ -126,279 +126,286 @@ public class ItemCountService : IItemCountService
     /// <inheritdoc />
     public ItemCounts GetItemCountsForNameItem(BaseItemKind kind, Guid id, BaseItemKind[] relatedItemKinds, InternalItemsQuery accessFilter)
     {
-        using var context = _dbProvider.CreateDbContext();
-
-        var item = context.BaseItems.AsNoTracking()
-            .Where(e => e.Id == id)
-            .Select(e => new { e.Name, e.CleanName })
-            .FirstOrDefault();
+        return GetItemCountsForNameItems(kind, [id], relatedItemKinds, accessFilter)[id];
+    }
 
-        if (item is null)
+    private static ItemValueType[] GetItemValueTypes(BaseItemKind kind)
+        => kind switch
         {
-            return new ItemCounts();
-        }
+            BaseItemKind.MusicArtist => [ItemValueType.Artist, ItemValueType.AlbumArtist],
+            BaseItemKind.Genre or BaseItemKind.MusicGenre => [ItemValueType.Genre],
+            BaseItemKind.Studio => [ItemValueType.Studios],
+            _ => []
+        };
 
-        IQueryable<BaseItemEntity> baseQuery;
-        switch (kind)
-        {
-            case BaseItemKind.Person:
-                baseQuery = ItemsById(context, context.PeopleBaseItemMap
-                    .AsNoTracking()
-                    .Where(m => m.People.Name == item.Name)
-                    .Select(m => m.ItemId));
-                break;
-            case BaseItemKind.MusicArtist:
-                baseQuery = ItemsById(context, context.ItemValuesMap
-                    .AsNoTracking()
-                    .Where(ivm => ivm.ItemValue.CleanValue == item.CleanName
-                        && (ivm.ItemValue.Type == ItemValueType.Artist || ivm.ItemValue.Type == ItemValueType.AlbumArtist))
-                    .Select(ivm => ivm.ItemId));
-                break;
-            case BaseItemKind.Genre:
-            case BaseItemKind.MusicGenre:
-                baseQuery = ItemsById(context, context.ItemValuesMap
-                    .AsNoTracking()
-                    .Where(ivm => ivm.ItemValue.CleanValue == item.CleanName
-                        && ivm.ItemValue.Type == ItemValueType.Genre)
-                    .Select(ivm => ivm.ItemId));
-                break;
-            case BaseItemKind.Studio:
-                baseQuery = ItemsById(context, context.ItemValuesMap
-                    .AsNoTracking()
-                    .Where(ivm => ivm.ItemValue.CleanValue == item.CleanName
-                        && ivm.ItemValue.Type == ItemValueType.Studios)
-                    .Select(ivm => ivm.ItemId));
-                break;
-            case BaseItemKind.Year:
-                if (int.TryParse(item.Name, NumberStyles.Integer, CultureInfo.InvariantCulture, out var year))
-                {
-                    baseQuery = context.BaseItems
-                        .AsNoTracking()
-                        .Where(e => e.ProductionYear == year);
-                }
-                else
-                {
-                    return new ItemCounts();
-                }
+    /// <inheritdoc />
+    public Dictionary<Guid, ItemCounts> GetItemCountsForNameItems(BaseItemKind kind, IReadOnlyList<Guid> ids, BaseItemKind[] relatedItemKinds, InternalItemsQuery accessFilter)
+    {
+        ArgumentNullException.ThrowIfNull(ids);
+        ArgumentNullException.ThrowIfNull(relatedItemKinds);
+        ArgumentNullException.ThrowIfNull(accessFilter);
 
-                break;
-            default:
-                return new ItemCounts();
+        var result = new Dictionary<Guid, ItemCounts>();
+        if (ids.Count == 0)
+        {
+            return result;
         }
 
-        var typeNames = relatedItemKinds.Select(k => _itemTypeLookup.BaseItemKindNames[k]).ToArray();
-        baseQuery = baseQuery.Where(e => typeNames.Contains(e.Type));
-
-        baseQuery = _queryHelpers.ApplyAccessFiltering(context, baseQuery, accessFilter);
+        using var context = _dbProvider.CreateDbContext();
 
-        var counts = baseQuery
-            .GroupBy(x => x.Type)
-            .Select(x => new { x.Key, Count = x.Count() })
+        var idsArray = ids as Guid[] ?? ids.ToArray();
+        var nameItems = context.BaseItems.AsNoTracking()
+            .WhereOneOrMany(idsArray, e => e.Id)
+            .Select(e => new NameItem(e.Id, e.Name, e.CleanName))
             .ToArray();
 
-        var result = BuildItemCounts(counts.Select(c => (c.Key, c.Count)));
-        var totalCount = result.ItemCount;
+        foreach (var id in ids)
+        {
+            result[id] = new ItemCounts();
+        }
 
-        if (kind is BaseItemKind.Studio or BaseItemKind.Genre or BaseItemKind.MusicGenre
-            && relatedItemKinds.Contains(BaseItemKind.Episode)
-            && relatedItemKinds.Contains(BaseItemKind.Series))
+        if (nameItems.Length == 0)
         {
-            var rolledUpEpisodeCount = CountEpisodesOfTaggedSeries(context, baseQuery, accessFilter, out var directEpisodeCount);
-            totalCount += rolledUpEpisodeCount - result.EpisodeCount + directEpisodeCount;
-            result.EpisodeCount = rolledUpEpisodeCount + directEpisodeCount;
+            return result;
         }
 
-        result.ItemCount = totalCount;
+        var typeNames = relatedItemKinds.Select(k => _itemTypeLookup.BaseItemKindNames[k]).ToArray();
+        var related = _queryHelpers.ApplyAccessFiltering(
+            context,
+            context.BaseItems.AsNoTracking().Where(e => typeNames.Contains(e.Type)),
+            accessFilter);
+
+        var valueTypes = GetItemValueTypes(kind);
+        if (valueTypes.Length > 0)
+        {
+            CountByItemValue(context, related, kind, relatedItemKinds, valueTypes, nameItems, result);
+        }
+        else if (kind == BaseItemKind.Person)
+        {
+            CountByPersonName(context, related, nameItems, result);
+        }
+        else if (kind == BaseItemKind.Year)
+        {
+            CountByProductionYear(related, nameItems, result);
+        }
 
         return result;
     }
 
-    private int CountEpisodesOfTaggedSeries(
+    private void CountByItemValue(
         JellyfinDbContext context,
-        IQueryable<BaseItemEntity> taggedItems,
-        InternalItemsQuery accessFilter,
-        out int unrelatedEpisodeCount)
+        IQueryable<BaseItemEntity> related,
+        BaseItemKind kind,
+        BaseItemKind[] relatedItemKinds,
+        ItemValueType[] valueTypes,
+        NameItem[] nameItems,
+        Dictionary<Guid, ItemCounts> result)
     {
-        var seriesTypeName = _itemTypeLookup.BaseItemKindNames[BaseItemKind.Series];
-        var episodeTypeName = _itemTypeLookup.BaseItemKindNames[BaseItemKind.Episode];
-
-        var taggedSeriesIds = taggedItems.Where(e => e.Type == seriesTypeName).Select(e => e.Id);
-        unrelatedEpisodeCount = taggedItems.Count(e => e.Type == episodeTypeName
-            && (e.SeriesId == null || !taggedSeriesIds.Contains(e.SeriesId.Value)));
-
-        // Materialised so the episode count drives off IX_BaseItems_SeriesId.
-        var seriesIds = taggedItems
-            .Where(e => e.Type == seriesTypeName)
-            .Select(e => e.Id)
+        var cleanNames = nameItems
+            .Select(n => n.CleanName)
+            .OfType<string>()
+            .Distinct(StringComparer.Ordinal)
             .ToArray();
 
-        if (seriesIds.Length == 0)
+        if (cleanNames.Length == 0)
         {
-            return 0;
+            return;
         }
 
-        var episodes = context.BaseItems.AsNoTracking()
-            .Where(e => e.Type == episodeTypeName && e.SeriesId != null)
-            .WhereOneOrMany(seriesIds, e => e.SeriesId!.Value);
+        var grouped = context.ItemValuesMap.AsNoTracking()
+            .Where(ivm => valueTypes.Contains(ivm.ItemValue.Type))
+            .WhereOneOrMany(cleanNames, ivm => ivm.ItemValue.CleanValue)
+            .Join(related, ivm => ivm.ItemId, e => e.Id, (ivm, e) => new { ivm.ItemValue.CleanValue, e.Type, e.Id })
+            .GroupBy(x => new { x.CleanValue, x.Type })
+            .Select(g => new { g.Key.CleanValue, g.Key.Type, Count = g.Select(x => x.Id).Distinct().Count() })
+            .ToArray();
 
-        return _queryHelpers.ApplyAccessFiltering(context, episodes, accessFilter).Count();
-    }
+        var byCleanName = grouped
+            .GroupBy(g => g.CleanValue, StringComparer.Ordinal)
+            .ToDictionary(g => g.Key, g => g.Select(x => (x.Type, x.Count)).ToArray(), StringComparer.Ordinal);
 
-    private ItemCounts BuildItemCounts(IEnumerable<(string Key, int Count)> counts)
-    {
-        var lookup = _itemTypeLookup.BaseItemKindNames;
-        var result = new ItemCounts();
-        var totalCount = 0;
+        var seriesTypeName = _itemTypeLookup.BaseItemKindNames[BaseItemKind.Series];
+        var episodeRollUp = RollsUpEpisodes(kind, relatedItemKinds)
+                && Array.Exists(grouped, g => string.Equals(g.Type, seriesTypeName, StringComparison.Ordinal))
+            ? CountEpisodesOfTaggedSeriesByCleanName(context, related, valueTypes, cleanNames)
+            : null;
 
-        foreach (var count in counts)
+        foreach (var nameItem in nameItems)
         {
-            totalCount += count.Count;
-
-            if (string.Equals(count.Key, lookup[BaseItemKind.MusicAlbum], StringComparison.Ordinal))
-            {
-                result.AlbumCount = count.Count;
-            }
-            else if (string.Equals(count.Key, lookup[BaseItemKind.MusicArtist], StringComparison.Ordinal))
-            {
-                result.ArtistCount = count.Count;
-            }
-            else if (string.Equals(count.Key, lookup[BaseItemKind.Episode], StringComparison.Ordinal))
-            {
-                result.EpisodeCount = count.Count;
-            }
-            else if (string.Equals(count.Key, lookup[BaseItemKind.Movie], StringComparison.Ordinal))
-            {
-                result.MovieCount = count.Count;
-            }
-            else if (string.Equals(count.Key, lookup[BaseItemKind.MusicVideo], StringComparison.Ordinal))
-            {
-                result.MusicVideoCount = count.Count;
-            }
-            else if (string.Equals(count.Key, lookup[BaseItemKind.LiveTvProgram], StringComparison.Ordinal))
-            {
-                result.ProgramCount = count.Count;
-            }
-            else if (string.Equals(count.Key, lookup[BaseItemKind.Series], StringComparison.Ordinal))
-            {
-                result.SeriesCount = count.Count;
-            }
-            else if (string.Equals(count.Key, lookup[BaseItemKind.Audio], StringComparison.Ordinal))
+            if (nameItem.CleanName is null || !byCleanName.TryGetValue(nameItem.CleanName, out var counts))
             {
-                result.SongCount = count.Count;
-            }
-            else if (string.Equals(count.Key, lookup[BaseItemKind.Trailer], StringComparison.Ordinal))
-            {
-                result.TrailerCount = count.Count;
-            }
-            else if (string.Equals(count.Key, lookup[BaseItemKind.BoxSet], StringComparison.Ordinal))
-            {
-                result.BoxSetCount = count.Count;
+                continue;
             }
-            else if (string.Equals(count.Key, lookup[BaseItemKind.Book], StringComparison.Ordinal))
+
+            var itemCounts = ItemCountBuilder.Build(_itemTypeLookup, counts);
+
+            if (episodeRollUp is not null)
             {
-                result.BookCount = count.Count;
-            }
-        }
+                var rollUp = episodeRollUp.GetValueOrDefault(nameItem.CleanName);
 
-        result.ItemCount = totalCount;
+                // Episodes of a tagged series count towards it even when untagged themselves, and
+                // a tagged episode of a tagged series must not be counted a second time.
+                var directEpisodeCount = itemCounts.EpisodeCount - rollUp.TaggedEpisodesOfTaggedSeries;
+                ItemCountBuilder.SetEpisodeCount(itemCounts, rollUp.EpisodesOfTaggedSeries + directEpisodeCount);
+            }
 
-        return result;
+            result[nameItem.Id] = itemCounts;
+        }
     }
 
-    private static ItemValueType[] GetItemValueTypes(BaseItemKind kind)
-        => kind switch
-        {
-            BaseItemKind.MusicArtist => [ItemValueType.Artist, ItemValueType.AlbumArtist],
-            BaseItemKind.Genre or BaseItemKind.MusicGenre => [ItemValueType.Genre],
-            BaseItemKind.Studio => [ItemValueType.Studios],
-            _ => []
-        };
-
-    /// <inheritdoc />
-    public Dictionary<Guid, ItemCounts> GetItemCountsForNameItems(BaseItemKind kind, IReadOnlyList<Guid> ids, BaseItemKind[] relatedItemKinds, InternalItemsQuery accessFilter)
+    private void CountByPersonName(
+        JellyfinDbContext context,
+        IQueryable<BaseItemEntity> related,
+        NameItem[] nameItems,
+        Dictionary<Guid, ItemCounts> result)
     {
-        ArgumentNullException.ThrowIfNull(ids);
-        ArgumentNullException.ThrowIfNull(relatedItemKinds);
+        var names = nameItems
+            .Select(n => n.Name)
+            .OfType<string>()
+            .Distinct(StringComparer.Ordinal)
+            .ToArray();
 
-        var result = new Dictionary<Guid, ItemCounts>();
-        if (ids.Count == 0)
+        if (names.Length == 0)
         {
-            return result;
+            return;
         }
 
-        // Only the kinds keyed by a cleaned item value can be grouped for every id in one query.
-        // Anything else, and the listing that rolls the episodes of a tagged series up into it,
-        // keeps the single item path, so a batch can never report a different number than it.
-        var valueTypes = GetItemValueTypes(kind);
-        var rollsUpEpisodes = kind is BaseItemKind.Studio or BaseItemKind.Genre or BaseItemKind.MusicGenre
-            && relatedItemKinds.Contains(BaseItemKind.Episode)
-            && relatedItemKinds.Contains(BaseItemKind.Series);
+        var grouped = context.PeopleBaseItemMap.AsNoTracking()
+            .WhereOneOrMany(names, m => m.People.Name)
+            .Join(related, m => m.ItemId, e => e.Id, (m, e) => new { m.People.Name, e.Type, e.Id })
+            .GroupBy(x => new { x.Name, x.Type })
+            // A person can be credited on one item more than once, in different roles.
+            .Select(g => new { g.Key.Name, g.Key.Type, Count = g.Select(x => x.Id).Distinct().Count() })
+            .ToArray();
+
+        ApplyGroupedCounts(nameItems, n => n.Name, grouped.Select(g => (g.Name, g.Type, g.Count)), result);
+    }
 
-        if (valueTypes.Length == 0 || rollsUpEpisodes)
+    private void CountByProductionYear(
+        IQueryable<BaseItemEntity> related,
+        NameItem[] nameItems,
+        Dictionary<Guid, ItemCounts> result)
+    {
+        var years = new List<int>();
+        foreach (var nameItem in nameItems)
         {
-            foreach (var id in ids)
+            if (int.TryParse(nameItem.Name, NumberStyles.Integer, CultureInfo.InvariantCulture, out var year)
+                && !years.Contains(year))
             {
-                result[id] = GetItemCountsForNameItem(kind, id, relatedItemKinds, accessFilter);
+                years.Add(year);
             }
-
-            return result;
         }
 
-        using var context = _dbProvider.CreateDbContext();
+        if (years.Count == 0)
+        {
+            return;
+        }
 
-        var nameItems = context.BaseItems.AsNoTracking()
-            .Where(e => ids.Contains(e.Id))
-            .Select(e => new { e.Id, e.CleanName })
+        // No join, so no row can be reached twice and a plain count is the distinct count.
+        var grouped = related
+            .Where(e => e.ProductionYear != null)
+            .WhereOneOrMany(years, e => e.ProductionYear!.Value)
+            .GroupBy(e => new { Year = e.ProductionYear!.Value, e.Type })
+            .Select(g => new { g.Key.Year, g.Key.Type, Count = g.Count() })
             .ToArray();
 
-        foreach (var id in ids)
+        var byYear = grouped
+            .GroupBy(g => g.Year)
+            .ToDictionary(g => g.Key, g => g.Select(x => (x.Type, x.Count)).ToArray());
+
+        foreach (var nameItem in nameItems)
         {
-            result[id] = new ItemCounts();
+            if (int.TryParse(nameItem.Name, NumberStyles.Integer, CultureInfo.InvariantCulture, out var year)
+                && byYear.TryGetValue(year, out var counts))
+            {
+                result[nameItem.Id] = ItemCountBuilder.Build(_itemTypeLookup, counts);
+            }
         }
+    }
 
-        var cleanNames = nameItems
-            .Select(n => n.CleanName)
-            .Where(n => n is not null)
-            .Distinct(StringComparer.Ordinal)
-            .ToArray();
+    private void ApplyGroupedCounts(
+        NameItem[] nameItems,
+        Func<NameItem, string?> keySelector,
+        IEnumerable<(string Key, string Type, int Count)> grouped,
+        Dictionary<Guid, ItemCounts> result)
+    {
+        var byKey = grouped
+            .GroupBy(g => g.Key, StringComparer.Ordinal)
+            .ToDictionary(g => g.Key, g => g.Select(x => (x.Type, x.Count)).ToArray(), StringComparer.Ordinal);
 
-        if (cleanNames.Length == 0)
+        foreach (var nameItem in nameItems)
         {
-            return result;
+            var key = keySelector(nameItem);
+            if (key is not null && byKey.TryGetValue(key, out var counts))
+            {
+                result[nameItem.Id] = ItemCountBuilder.Build(_itemTypeLookup, counts);
+            }
         }
+    }
 
-        var typeNames = relatedItemKinds.Select(k => _itemTypeLookup.BaseItemKindNames[k]).ToArray();
+    private static bool RollsUpEpisodes(BaseItemKind kind, BaseItemKind[] relatedItemKinds)
+        => kind is BaseItemKind.Studio or BaseItemKind.Genre or BaseItemKind.MusicGenre
+            && relatedItemKinds.Contains(BaseItemKind.Episode)
+            && relatedItemKinds.Contains(BaseItemKind.Series);
 
-        var related = _queryHelpers.ApplyAccessFiltering(
-            context,
-            context.BaseItems.AsNoTracking().Where(e => typeNames.Contains(e.Type)),
-            accessFilter);
+    private Dictionary<string, (int EpisodesOfTaggedSeries, int TaggedEpisodesOfTaggedSeries)> CountEpisodesOfTaggedSeriesByCleanName(
+        JellyfinDbContext context,
+        IQueryable<BaseItemEntity> related,
+        ItemValueType[] valueTypes,
+        string[] cleanNames)
+    {
+        var seriesTypeName = _itemTypeLookup.BaseItemKindNames[BaseItemKind.Series];
+        var episodeTypeName = _itemTypeLookup.BaseItemKindNames[BaseItemKind.Episode];
 
-        var grouped = context.ItemValuesMap.AsNoTracking()
-            .Where(ivm => valueTypes.Contains(ivm.ItemValue.Type) && cleanNames.Contains(ivm.ItemValue.CleanValue))
-            .Join(related, ivm => ivm.ItemId, e => e.Id, (ivm, e) => new { ivm.ItemValue.CleanValue, e.Type })
-            .GroupBy(x => new { x.CleanValue, x.Type })
-            .Select(g => new { g.Key.CleanValue, g.Key.Type, Count = g.Count() })
+        var taggedValues = context.ItemValuesMap.AsNoTracking()
+            .Where(ivm => valueTypes.Contains(ivm.ItemValue.Type))
+            .WhereOneOrMany(cleanNames, ivm => ivm.ItemValue.CleanValue);
+
+        // The series carrying each clean name. Distinct, because one item can be mapped to the
+        // same clean name once per value type.
+        var taggedSeries = taggedValues
+            .Join(
+                related.Where(e => e.Type == seriesTypeName),
+                ivm => ivm.ItemId,
+                e => e.Id,
+                (ivm, e) => new { ivm.ItemValue.CleanValue, SeriesId = e.Id })
+            .Distinct();
+
+        var episodes = related.Where(e => e.Type == episodeTypeName && e.SeriesId != null);
+
+        var episodesOfTaggedSeries = taggedSeries
+            .Join(episodes, s => s.SeriesId, e => e.SeriesId!.Value, (s, e) => new { s.CleanValue, e.Id })
+            .GroupBy(x => x.CleanValue)
+            .Select(g => new { CleanValue = g.Key, Count = g.Select(x => x.Id).Distinct().Count() })
             .ToArray();
 
-        var byCleanName = grouped
-            .GroupBy(g => g.CleanValue, StringComparer.Ordinal)
-            .ToDictionary(g => g.Key, g => g.Select(x => (x.Type, x.Count)).ToArray(), StringComparer.Ordinal);
+        // Episodes that carry the clean name themselves *and* belong to a series carrying it. The
+        // roll-up already counts those, so they have to come off the directly tagged ones.
+        var taggedEpisodesOfTaggedSeries = taggedValues
+            .Join(episodes, ivm => ivm.ItemId, e => e.Id, (ivm, e) => new { ivm.ItemValue.CleanValue, e.Id, e.SeriesId })
+            .Join(
+                taggedSeries,
+                e => new { e.CleanValue, SeriesId = e.SeriesId!.Value },
+                s => new { s.CleanValue, s.SeriesId },
+                (e, s) => new { e.CleanValue, e.Id })
+            .GroupBy(x => x.CleanValue)
+            .Select(g => new { CleanValue = g.Key, Count = g.Select(x => x.Id).Distinct().Count() })
+            .ToArray();
 
-        foreach (var nameItem in nameItems)
+        var taggedLookup = taggedEpisodesOfTaggedSeries
+            .ToDictionary(x => x.CleanValue, x => x.Count, StringComparer.Ordinal);
+
+        // Every clean name in taggedLookup came from an episode of a tagged series, so it always
+        // has a row in episodesOfTaggedSeries too - no second merge pass is needed.
+        var result = new Dictionary<string, (int EpisodesOfTaggedSeries, int TaggedEpisodesOfTaggedSeries)>(StringComparer.Ordinal);
+        foreach (var entry in episodesOfTaggedSeries)
         {
-            if (nameItem.CleanName is not null && byCleanName.TryGetValue(nameItem.CleanName, out var counts))
-            {
-                result[nameItem.Id] = BuildItemCounts(counts);
-            }
+            result[entry.CleanValue] = (entry.Count, taggedLookup.GetValueOrDefault(entry.CleanValue));
         }
 
         return result;
     }
 
-    private static IQueryable<BaseItemEntity> ItemsById(JellyfinDbContext context, IQueryable<Guid> itemIds)
-        => context.BaseItems.AsNoTracking().Where(e => itemIds.Contains(e.Id));
-
     /// <inheritdoc/>
     public int GetPlayedCount(InternalItemsQuery filter, Guid ancestorId)
     {
@@ -724,4 +731,12 @@ public class ItemCountService : IItemCountService
 
         return result is null ? (0, 0) : (result.Played, result.Total);
     }
+
+    /// <summary>
+    /// A by-name item, reduced to the three columns the counting keys off.
+    /// </summary>
+    /// <param name="Id">The id of the by-name item.</param>
+    /// <param name="Name">The name of the by-name item.</param>
+    /// <param name="CleanName">The cleaned name of the by-name item.</param>
+    private sealed record NameItem(Guid Id, string? Name, string? CleanName);
 }
diff --git a/MediaBrowser.Controller/Library/ILibraryManager.cs b/MediaBrowser.Controller/Library/ILibraryManager.cs
index 382559384a..ac6df54949 100644
--- a/MediaBrowser.Controller/Library/ILibraryManager.cs
+++ b/MediaBrowser.Controller/Library/ILibraryManager.cs
@@ -760,8 +760,9 @@ namespace MediaBrowser.Controller.Library
         ItemCounts GetItemCountsForNameItem(BaseItemKind kind, Guid id, BaseItemKind[] relatedItemKinds, User? user);
 
         /// <summary>
-        /// Gets item counts for several "by-name" items of the same kind in one query, instead of
-        /// one query per item.
+        /// Gets item counts for several "by-name" items of the same kind. Kinds keyed by a cleaned
+        /// item value - artists, genres and studios - are answered in one set of queries for the
+        /// whole batch; the rest fall back to one query per item.
         /// </summary>
         /// <param name="kind">The kind of the name items.</param>
         /// <param name="ids">The IDs of the name items.</param>
diff --git a/MediaBrowser.Controller/Persistence/IItemCountService.cs b/MediaBrowser.Controller/Persistence/IItemCountService.cs
index 20b5cbe603..14c422cb60 100644
--- a/MediaBrowser.Controller/Persistence/IItemCountService.cs
+++ b/MediaBrowser.Controller/Persistence/IItemCountService.cs
@@ -37,7 +37,9 @@ public interface IItemCountService
     ItemCounts GetItemCountsForNameItem(BaseItemKind kind, Guid id, BaseItemKind[] relatedItemKinds, InternalItemsQuery accessFilter);
 
     /// <summary>
-    /// Gets item counts for several "by-name" items of the same kind in one query.
+    /// Gets item counts for several "by-name" items of the same kind. Kinds keyed by a cleaned
+    /// item value - artists, genres and studios - are answered in one set of queries for the whole
+    /// batch; the rest fall back to one query per id.
     /// </summary>
     /// <param name="kind">The kind of the name items.</param>
     /// <param name="ids">The IDs of the name items.</param>
diff --git a/tests/Jellyfin.Server.Implementations.Tests/Item/BaseItemRepositoryByNameItemCountsTests.cs b/tests/Jellyfin.Server.Implementations.Tests/Item/BaseItemRepositoryByNameItemCountsTests.cs
new file mode 100644
index 0000000000..298340d1b0
--- /dev/null
+++ b/tests/Jellyfin.Server.Implementations.Tests/Item/BaseItemRepositoryByNameItemCountsTests.cs
@@ -0,0 +1,215 @@
+using System;
+using Emby.Server.Implementations.Data;
+using Jellyfin.Database.Implementations.Entities;
+using Jellyfin.Server.Implementations.Item;
+using MediaBrowser.Controller.Dto;
+using MediaBrowser.Controller.Entities;
+using MediaBrowser.Model.Querying;
+using Xunit;
+using BaseItemKind = Jellyfin.Data.Enums.BaseItemKind;
+
+namespace Jellyfin.Server.Implementations.Tests.Item;
+
+/// <summary>
+/// The by-name listings count what a cleaned value is attached to by joining ItemValuesMap to
+/// BaseItems. One item can reach the same clean value through more than one value row, so the
+/// join has to be counted per distinct item; counting rows reports a multiple of the truth.
+/// </summary>
+public sealed class BaseItemRepositoryByNameItemCountsTests : SqliteDbTestFixture
+{
+    private readonly BaseItemRepository _repository;
+    private readonly ItemTypeLookup _itemTypeLookup;
+
+    public BaseItemRepositoryByNameItemCountsTests()
+    {
+        _itemTypeLookup = new ItemTypeLookup();
+        _repository = CreateBaseItemRepository(_itemTypeLookup);
+    }
+
+    [Fact]
+    public void GetAllArtists_AlbumCreditedAsArtistAndAlbumArtist_CountsTheAlbumOnce()
+    {
+        // GetAllArtists spans both credit types, so an album whose artist is also its album artist
+        // reaches the one clean value through two rows.
+        SeedArtistWithAlbum(ItemValueType.Artist, ItemValueType.AlbumArtist);
+
+        var result = _repository.GetAllArtists(CreateCountingQuery());
+
+        var (_, counts) = Assert.Single(result.Items);
+        Assert.NotNull(counts);
+        Assert.Equal(1, counts.AlbumCount);
+        Assert.Equal(1, counts.ItemCount);
+    }
+
+    [Fact]
+    public void GetAlbumArtists_TwoValueRowsCleaningToOneName_CountsTheAlbumOnce()
+    {
+        // The shape that actually reaches users: only (Type, Value) is unique, so two differently
+        // cased credits of one type both clean down to a single name and both map the album.
+        SeedArtistWithAlbum(ItemValueType.AlbumArtist, ItemValueType.AlbumArtist);
+
+        var result = _repository.GetAlbumArtists(CreateCountingQuery());
+
+        var (_, counts) = Assert.Single(result.Items);
+        Assert.NotNull(counts);
+        Assert.Equal(1, counts.AlbumCount);
+    }
+
+    [Fact]
+    public void GetArtists_TwoValueRowsCleaningToOneName_CountsTheAlbumOnce()
+    {
+        SeedArtistWithAlbum(ItemValueType.Artist, ItemValueType.Artist);
+
+        var result = _repository.GetArtists(CreateCountingQuery());
+
+        var (_, counts) = Assert.Single(result.Items);
+        Assert.NotNull(counts);
+        Assert.Equal(1, counts.AlbumCount);
+    }
+
+    [Theory]
+    [InlineData(BaseItemKind.Book)]
+    [InlineData(BaseItemKind.BoxSet)]
+    public void GetGenres_TaggedBookOrBoxSet_CountsIt(BaseItemKind kind)
+    {
+        // The listing used to dispatch only nine of the eleven counted types, so a genre on a book
+        // or a box set read as zero in a list and as one on the genre's own page.
+        SeedGenreWith(kind);
+
+        var result = _repository.GetGenres(CreateCountingQuery());
+
+        var (_, counts) = Assert.Single(result.Items);
+        Assert.NotNull(counts);
+        Assert.Equal(1, kind == BaseItemKind.Book ? counts.BookCount : counts.BoxSetCount);
+        Assert.Equal(1, counts.ItemCount);
+    }
+
+    /// <summary>
+    /// Seeds one genre carried by a single item of the given kind.
+    /// </summary>
+    /// <param name="kind">The kind of the tagged item.</param>
+    private void SeedGenreWith(BaseItemKind kind)
+    {
+        const string Name = "Reference";
+        const string CleanName = "reference";
+
+        using var ctx = CreateDbContext();
+
+        var genreId = Guid.Parse("dddddddd-0000-0000-0000-000000000001");
+        var taggedId = Guid.Parse("eeeeeeee-0000-0000-0000-000000000001");
+
+        ctx.BaseItems.Add(new BaseItemEntity
+        {
+            Id = genreId,
+            Type = _itemTypeLookup.BaseItemKindNames[BaseItemKind.Genre],
+            Name = Name,
+            CleanName = CleanName,
+            PresentationUniqueKey = genreId.ToString("N"),
+            IsFolder = true,
+            IsVirtualItem = false
+        });
+
+        var tagged = new BaseItemEntity
+        {
+            Id = taggedId,
+            Type = _itemTypeLookup.BaseItemKindNames[kind],
+            Name = "Tagged",
+            CleanName = "tagged",
+            PresentationUniqueKey = taggedId.ToString("N"),
+            IsFolder = false,
+            IsVirtualItem = false
+        };
+        ctx.BaseItems.Add(tagged);
+
+        var itemValue = new ItemValue
+        {
+            ItemValueId = Guid.Parse("ffffffff-0000-0000-0000-000000000001"),
+            Type = ItemValueType.Genre,
+            Value = Name,
+            CleanValue = CleanName
+        };
+
+        ctx.ItemValues.Add(itemValue);
+        ctx.ItemValuesMap.Add(new ItemValueMap
+        {
+            ItemId = taggedId,
+            ItemValueId = itemValue.ItemValueId,
+            Item = tagged,
+            ItemValue = itemValue
+        });
+
+        ctx.SaveChanges();
+    }
+
+    private static InternalItemsQuery CreateCountingQuery()
+    {
+        return new InternalItemsQuery(new User("test", "auth", "reset"))
+        {
+            DtoOptions = new DtoOptions(true) { Fields = [ItemFields.ItemCounts] }
+        };
+    }
+
+    /// <summary>
+    /// Seeds one artist and a single album mapped to that artist's clean name through two value
+    /// rows of the given types.
+    /// </summary>
+    /// <param name="first">The type of the first value row.</param>
+    /// <param name="second">The type of the second value row.</param>
+    private void SeedArtistWithAlbum(ItemValueType first, ItemValueType second)
+    {
+        const string Name = "Tangerine Dream";
+        const string CleanName = "tangerine dream";
+
+        using var ctx = CreateDbContext();
+
+        var artistId = Guid.Parse("aaaaaaaa-0000-0000-0000-000000000001");
+        var albumId = Guid.Parse("bbbbbbbb-0000-0000-0000-000000000001");
+
+        ctx.BaseItems.Add(new BaseItemEntity
+        {
+            Id = artistId,
+            Type = _itemTypeLookup.BaseItemKindNames[BaseItemKind.MusicArtist],
+            Name = Name,
+            CleanName = CleanName,
+            PresentationUniqueKey = artistId.ToString("N"),
+            IsFolder = true,
+            IsVirtualItem = false
+        });
+
+        var album = new BaseItemEntity
+        {
+            Id = albumId,
+            Type = _itemTypeLookup.BaseItemKindNames[BaseItemKind.MusicAlbum],
+            Name = "Phaedra",
+            CleanName = "phaedra",
+            PresentationUniqueKey = albumId.ToString("N"),
+            IsFolder = true,
+            IsVirtualItem = false
+        };
+        ctx.BaseItems.Add(album);
+
+        var types = new[] { first, second };
+        for (var i = 0; i < types.Length; i++)
+        {
+            var itemValue = new ItemValue
+            {
+                ItemValueId = Guid.Parse($"cccccccc-0000-0000-0000-{i:D12}"),
+                Type = types[i],
+                // Distinct values, one clean name: exactly what the unique index permits.
+                Value = i == 0 ? Name : Name.ToUpperInvariant(),
+                CleanValue = CleanName
+            };
+
+            ctx.ItemValues.Add(itemValue);
+            ctx.ItemValuesMap.Add(new ItemValueMap
+            {
+                ItemId = albumId,
+                ItemValueId = itemValue.ItemValueId,
+                Item = album,
+                ItemValue = itemValue
+            });
+        }
+
+        ctx.SaveChanges();
+    }
+}
diff --git a/tests/Jellyfin.Server.Implementations.Tests/Item/ItemCountServiceTests.cs b/tests/Jellyfin.Server.Implementations.Tests/Item/ItemCountServiceTests.cs
index d0e29e5142..ff683dc57a 100644
--- a/tests/Jellyfin.Server.Implementations.Tests/Item/ItemCountServiceTests.cs
+++ b/tests/Jellyfin.Server.Implementations.Tests/Item/ItemCountServiceTests.cs
@@ -15,6 +15,7 @@ using MediaBrowser.Controller.Library;
 using MediaBrowser.Controller.Persistence;
 using Microsoft.Data.Sqlite;
 using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Logging.Abstractions;
 using Moq;
 using Xunit;
@@ -28,6 +29,8 @@ public sealed class ItemCountServiceTests : IDisposable
     private readonly DbContextOptions<JellyfinDbContext> _dbOptions;
     private readonly IApplicationPaths _applicationPaths;
     private readonly ItemCountService _service;
+    private int _contextsCreated;
+    private List<string>? _capturedSql;
 
     public ItemCountServiceTests()
     {
@@ -38,6 +41,7 @@ public sealed class ItemCountServiceTests : IDisposable
 
         _dbOptions = new DbContextOptionsBuilder<JellyfinDbContext>()
             .UseSqlite(_connection)
+            .LogTo(CaptureStatement, LogLevel.Information)
             .Options;
 
         using (var context = CreateDbContext())
@@ -46,7 +50,11 @@ public sealed class ItemCountServiceTests : IDisposable
         }
 
         var factory = new Mock<IDbContextFactory<JellyfinDbContext>>();
-        factory.Setup(f => f.CreateDbContext()).Returns(CreateDbContext);
+        factory.Setup(f => f.CreateDbContext()).Returns(() =>
+        {
+            _contextsCreated++;
+            return CreateDbContext();
+        });
 
         var queryHelpers = new Mock<IItemQueryHelpers>();
         queryHelpers
@@ -83,6 +91,14 @@ public sealed class ItemCountServiceTests : IDisposable
         _connection.Dispose();
     }
 
+    private void CaptureStatement(string message)
+    {
+        if (_capturedSql is not null && message.Contains("SELECT", StringComparison.Ordinal))
+        {
+            _capturedSql.Add(message[message.IndexOf("SELECT", StringComparison.Ordinal)..]);
+        }
+    }
+
     [Fact]
     public void GetChildCountBatch_LargeParentIdSet_DoesNotExceedSqliteVariableLimit()
     {
@@ -395,6 +411,597 @@ public sealed class ItemCountServiceTests : IDisposable
         Assert.Equal(0, batch[unknown].ItemCount);
     }
 
+    [Fact]
+    public void GetItemCountsForNameItems_ArtistTaggedTwiceOnOneAlbum_CountsTheAlbumOnce()
+    {
+        // An album whose artist is also its album artist maps to the same artist twice.
+        var artistId = SeedArtistWithAlbum();
+
+        var filter = new InternalItemsQuery();
+        BaseItemKind[] related = [BaseItemKind.MusicAlbum];
+
+        var batch = _service.GetItemCountsForNameItems(BaseItemKind.MusicArtist, [artistId], related, filter);
+        var single = _service.GetItemCountsForNameItem(BaseItemKind.MusicArtist, artistId, related, filter);
+
+        Assert.Equal(1, batch[artistId].AlbumCount);
+        Assert.Equal(single.AlbumCount, batch[artistId].AlbumCount);
+        Assert.Equal(single.ItemCount, batch[artistId].ItemCount);
+    }
+
+    /// <summary>
+    /// Seeds one artist and a single album tagged with it as both artist and album artist.
+    /// </summary>
+    /// <returns>The id of the seeded artist.</returns>
+    private Guid SeedArtistWithAlbum()
+    {
+        const string Name = "artist-0";
+        var artistId = Guid.NewGuid();
+        var albumId = Guid.NewGuid();
+
+        using var context = CreateDbContext();
+
+        var artist = CreateItem(artistId);
+        artist.Type = "MusicArtist";
+        artist.Name = Name;
+        artist.CleanName = Name;
+        context.BaseItems.Add(artist);
+
+        var album = CreateItem(albumId);
+        album.Type = "MusicAlbum";
+        context.BaseItems.Add(album);
+        context.SaveChanges();
+
+        foreach (var type in new[] { ItemValueType.Artist, ItemValueType.AlbumArtist })
+        {
+            var itemValue = new ItemValue
+            {
+                ItemValueId = Guid.NewGuid(),
+                Type = type,
+                Value = Name,
+                CleanValue = Name
+            };
+            context.ItemValues.Add(itemValue);
+            context.SaveChanges();
+
+            context.ItemValuesMap.Add(new ItemValueMap
+            {
+                ItemId = albumId,
+                ItemValueId = itemValue.ItemValueId,
+                Item = null!,
+                ItemValue = null!
+            });
+        }
+
+        context.SaveChanges();
+
+        return artistId;
+    }
+
+    [Fact]
+    public void GetItemCountsForNameItems_LargeIdSet_DoesNotExceedSqliteVariableLimit()
+    {
+        // Seeded rather than random, so the clean names of every one of them reach the second
+        // query's IN list and the join behind it, instead of stopping at the empty-name return.
+        var seeded = SeedArtists(50, out var taggedArtistId);
+
+        var ids = seeded.Concat(Enumerable.Range(0, 40_000).Select(_ => Guid.NewGuid())).ToList();
+
+        var batch = _service.GetItemCountsForNameItems(
+            BaseItemKind.MusicArtist,
+            ids,
+            [BaseItemKind.MusicAlbum],
+            new InternalItemsQuery());
+
+        Assert.Equal(ids.Count, batch.Count);
+
+        // And the grouped query really ran, rather than every id coming back zeroed.
+        Assert.Equal(1, batch[taggedArtistId].AlbumCount);
+    }
+
+    [Fact]
+    public void GetItemCountsForNameItems_QueryShape_DoesNotVaryWithBatchSize()
+    {
+        // Every id list has to be bound as one parameter rather than one placeholder each: that is
+        // what keeps the statement off the SQLite variable ceiling and out of a per-size entry in
+        // EF's compiled query cache. Identical SQL for two batch sizes is exactly that property.
+        var seeded = SeedArtists(6, out _);
+
+        var small = CaptureSql(() => _service.GetItemCountsForNameItems(
+            BaseItemKind.MusicArtist, seeded.Take(2).ToList(), [BaseItemKind.MusicAlbum], new InternalItemsQuery()));
+
+        var large = CaptureSql(() => _service.GetItemCountsForNameItems(
+            BaseItemKind.MusicArtist, seeded, [BaseItemKind.MusicAlbum], new InternalItemsQuery()));
+
+        Assert.NotEmpty(small);
+        Assert.Equal(small, large);
+    }
+
+    private List<string> CaptureSql(Action action)
+    {
+        _capturedSql = [];
+        try
+        {
+            action();
+            return _capturedSql;
+        }
+        finally
+        {
+            _capturedSql = null;
+        }
+    }
+
+    /// <summary>
+    /// Seeds the requested number of artists, each with a clean name of its own, one of which is
+    /// credited on a single album.
+    /// </summary>
+    /// <param name="count">The number of artists to seed.</param>
+    /// <param name="taggedArtistId">The id of the artist credited on an album.</param>
+    /// <returns>The ids of the seeded artists.</returns>
+    private List<Guid> SeedArtists(int count, out Guid taggedArtistId)
+    {
+        var ids = new List<Guid>(count);
+        using var context = CreateDbContext();
+
+        ItemValue? taggedValue = null;
+        taggedArtistId = Guid.Empty;
+
+        for (var i = 0; i < count; i++)
+        {
+            var name = "bulk-artist-" + i.ToString(CultureInfo.InvariantCulture);
+            var artistId = Guid.NewGuid();
+            ids.Add(artistId);
+
+            var artist = CreateItem(artistId);
+            artist.Type = "MusicArtist";
+            artist.Name = name;
+            artist.CleanName = name;
+            context.BaseItems.Add(artist);
+
+            if (i == 0)
+            {
+                taggedArtistId = artistId;
+                taggedValue = new ItemValue
+                {
+                    ItemValueId = Guid.NewGuid(),
+                    Type = ItemValueType.Artist,
+                    Value = name,
+                    CleanValue = name
+                };
+                context.ItemValues.Add(taggedValue);
+            }
+        }
+
+        context.SaveChanges();
+
+        var albumId = Guid.NewGuid();
+        var album = CreateItem(albumId);
+        album.Type = "MusicAlbum";
+        context.BaseItems.Add(album);
+        context.SaveChanges();
+
+        Tag(context, albumId, taggedValue!.ItemValueId);
+        context.SaveChanges();
+
+        return ids;
+    }
+
+    [Fact]
+    public void GetItemCountsForNameItems_KindWithoutItemValues_FallsBackToTheSingleItemPath()
+    {
+        // Year is keyed by ProductionYear rather than a cleaned item value, so it cannot be grouped.
+        var yearId = Guid.NewGuid();
+
+        using (var context = CreateDbContext())
+        {
+            var year = CreateItem(yearId);
+            year.Type = "Year";
+            year.Name = "2001";
+            year.CleanName = "2001";
+            context.BaseItems.Add(year);
+
+            for (var i = 0; i < 2; i++)
+            {
+                var movie = CreateItem(Guid.NewGuid());
+                movie.Type = "Movie";
+                movie.IsFolder = false;
+                movie.ProductionYear = 2001;
+                context.BaseItems.Add(movie);
+            }
+
+            context.SaveChanges();
+        }
+
+        var filter = new InternalItemsQuery();
+        BaseItemKind[] related = [BaseItemKind.Movie];
+
+        var batch = _service.GetItemCountsForNameItems(BaseItemKind.Year, [yearId], related, filter);
+        var single = _service.GetItemCountsForNameItem(BaseItemKind.Year, yearId, related, filter);
+
+        Assert.Equal(2, batch[yearId].MovieCount);
+        Assert.Equal(single.MovieCount, batch[yearId].MovieCount);
+    }
+
+    [Fact]
+    public void GetItemCountsForNameItems_PeopleAndYears_AreBatchedToo()
+    {
+        var (personIds, yearIds) = SeedPeopleAndYears();
+
+        var filter = new InternalItemsQuery();
+        BaseItemKind[] related = [BaseItemKind.Movie];
+
+        foreach (var (kind, ids) in new[] { (BaseItemKind.Person, personIds), (BaseItemKind.Year, yearIds) })
+        {
+            var contextsBefore = _contextsCreated;
+            var batch = _service.GetItemCountsForNameItems(kind, ids, related, filter);
+
+            // These two used to be answered one query per id; only the value keyed kinds batched.
+            Assert.Equal(1, _contextsCreated - contextsBefore);
+
+            Assert.Equal(ids.Count, batch.Count);
+            Assert.Equal(2, batch[ids[0]].MovieCount);
+            Assert.Equal(1, batch[ids[1]].MovieCount);
+
+            foreach (var id in ids)
+            {
+                var single = _service.GetItemCountsForNameItem(kind, id, related, filter);
+                Assert.Equal(single.MovieCount, batch[id].MovieCount);
+                Assert.Equal(single.ItemCount, batch[id].ItemCount);
+            }
+        }
+    }
+
+    /// <summary>
+    /// Seeds two people and two years, the first of each on two movies and the second on one.
+    /// </summary>
+    /// <returns>The ids of the seeded people and years.</returns>
+    private (List<Guid> PersonIds, List<Guid> YearIds) SeedPeopleAndYears()
+    {
+        var personIds = new List<Guid>();
+        var yearIds = new List<Guid>();
+
+        using var context = CreateDbContext();
+
+        for (var i = 0; i < 2; i++)
+        {
+            var personName = "person-" + i.ToString(CultureInfo.InvariantCulture);
+            var personId = Guid.NewGuid();
+            personIds.Add(personId);
+
+            var person = CreateItem(personId);
+            person.Type = "Person";
+            person.Name = personName;
+            person.CleanName = personName;
+            context.BaseItems.Add(person);
+
+            var people = new People { Id = Guid.NewGuid(), Name = personName };
+            context.Peoples.Add(people);
+
+            var year = 2000 + i;
+            var yearId = Guid.NewGuid();
+            yearIds.Add(yearId);
+
+            var yearItem = CreateItem(yearId);
+            yearItem.Type = "Year";
+            yearItem.Name = year.ToString(CultureInfo.InvariantCulture);
+            yearItem.CleanName = yearItem.Name;
+            context.BaseItems.Add(yearItem);
+            context.SaveChanges();
+
+            // Two movies for the first of each, one for the second.
+            for (var m = 0; m < 2 - i; m++)
+            {
+                var movieId = Guid.NewGuid();
+                var movie = CreateItem(movieId);
+                movie.Type = "Movie";
+                movie.IsFolder = false;
+                movie.ProductionYear = year;
+                context.BaseItems.Add(movie);
+                context.SaveChanges();
+
+                context.PeopleBaseItemMap.Add(new PeopleBaseItemMap
+                {
+                    ItemId = movieId,
+                    PeopleId = people.Id,
+                    Item = null!,
+                    People = null!,
+                    Role = "Actor",
+                    ListOrder = m,
+                    SortOrder = m
+                });
+            }
+
+            context.SaveChanges();
+        }
+
+        return (personIds, yearIds);
+    }
+
+    [Theory]
+    // The set the by-name listing actually asks for: it rolls the episodes of a tagged series up
+    // into the genre, which is the case the batch has to reproduce query for query.
+    [InlineData(BaseItemKind.Episode, BaseItemKind.Series, BaseItemKind.Movie)]
+    // And the same seeded data without the roll-up, which takes the plain grouped path.
+    [InlineData(BaseItemKind.Movie, BaseItemKind.Series, BaseItemKind.MusicAlbum)]
+    public void GetItemCountsForNameItems_TaggedSeriesAndEpisodes_MatchesCountingEachNameItemOnItsOwn(
+        BaseItemKind first,
+        BaseItemKind second,
+        BaseItemKind third)
+    {
+        var genres = SeedGenresTaggingSeriesAndEpisodes();
+
+        var filter = new InternalItemsQuery();
+        BaseItemKind[] related = [first, second, third];
+
+        var batch = _service.GetItemCountsForNameItems(BaseItemKind.Genre, genres, related, filter);
+
+        Assert.Equal(genres.Count, batch.Count);
+
+        foreach (var genreId in genres)
+        {
+            var single = _service.GetItemCountsForNameItem(BaseItemKind.Genre, genreId, related, filter);
+
+            Assert.Equal(single.EpisodeCount, batch[genreId].EpisodeCount);
+            Assert.Equal(single.SeriesCount, batch[genreId].SeriesCount);
+            Assert.Equal(single.MovieCount, batch[genreId].MovieCount);
+            Assert.Equal(single.ItemCount, batch[genreId].ItemCount);
+        }
+    }
+
+    [Fact]
+    public void GetItemCountsForNameItems_TaggedSeries_RollsEpisodesUpIntoTheGenre()
+    {
+        var genres = SeedGenresTaggingSeriesAndEpisodes();
+
+        var contextsBefore = _contextsCreated;
+
+        var batch = _service.GetItemCountsForNameItems(
+            BaseItemKind.Genre,
+            genres,
+            [BaseItemKind.Episode, BaseItemKind.Series, BaseItemKind.Movie],
+            new InternalItemsQuery());
+
+        // The whole point of the batch: one context for every genre on the page, not one each.
+        // The roll-up used to force this shape back onto the single item path.
+        Assert.Equal(1, _contextsCreated - contextsBefore);
+
+        // "rolled": one tagged series of two episodes, one of which carries the genre itself, plus
+        // a loose tagged episode of an untagged series. The tagged episode of the tagged series
+        // must not be counted twice.
+        Assert.Equal(3, batch[genres[0]].EpisodeCount);
+        Assert.Equal(1, batch[genres[0]].SeriesCount);
+
+        // "loose": a tagged episode whose series carries no genre at all.
+        Assert.Equal(1, batch[genres[1]].EpisodeCount);
+        Assert.Equal(0, batch[genres[1]].SeriesCount);
+
+        // "empty": tags nothing.
+        Assert.Equal(0, batch[genres[2]].EpisodeCount);
+    }
+
+    [Fact]
+    public void GetItemCountsForNameItems_EpisodeAndItsSeriesTaggedDifferently_KeepsTheGenresApart()
+    {
+        var seriesId = Guid.NewGuid();
+        var episodeId = Guid.NewGuid();
+        var genreIds = new List<Guid>();
+
+        using (var context = CreateDbContext())
+        {
+            var values = new Dictionary<string, Guid>(StringComparer.Ordinal);
+            foreach (var name in new[] { "on-series", "on-episode" })
+            {
+                var genreId = Guid.NewGuid();
+                genreIds.Add(genreId);
+
+                var genre = CreateItem(genreId);
+                genre.Type = "Genre";
+                genre.Name = name;
+                genre.CleanName = name;
+                context.BaseItems.Add(genre);
+
+                var itemValue = new ItemValue
+                {
+                    ItemValueId = Guid.NewGuid(),
+                    Type = ItemValueType.Genre,
+                    Value = name,
+                    CleanValue = name
+                };
+                context.ItemValues.Add(itemValue);
+                values[name] = itemValue.ItemValueId;
+            }
+
+            var series = CreateItem(seriesId);
+            series.Type = "Series";
+            context.BaseItems.Add(series);
+            context.BaseItems.Add(CreateEpisode(episodeId, seriesId));
+            context.SaveChanges();
+
+            Tag(context, seriesId, values["on-series"]);
+            Tag(context, episodeId, values["on-episode"]);
+            context.SaveChanges();
+        }
+
+        var filter = new InternalItemsQuery();
+        BaseItemKind[] related = [BaseItemKind.Episode, BaseItemKind.Series, BaseItemKind.Movie];
+
+        var batch = _service.GetItemCountsForNameItems(BaseItemKind.Genre, genreIds, related, filter);
+
+        // The episode rolls up into the genre on its series.
+        Assert.Equal(1, batch[genreIds[0]].EpisodeCount);
+
+        // Its own genre is carried by no series, so the episode stays a direct count there. Keyed
+        // on the series id alone the episode would be subtracted here and this would read 0.
+        Assert.Equal(1, batch[genreIds[1]].EpisodeCount);
+        Assert.Equal(0, batch[genreIds[1]].SeriesCount);
+
+        foreach (var genreId in genreIds)
+        {
+            var single = _service.GetItemCountsForNameItem(BaseItemKind.Genre, genreId, related, filter);
+            Assert.Equal(single.EpisodeCount, batch[genreId].EpisodeCount);
+            Assert.Equal(single.ItemCount, batch[genreId].ItemCount);
+        }
+    }
+
+    [Fact]
+    public void GetItemCountsForNameItems_TwoNameItemsSharingACleanName_BothGetTheCounts()
+    {
+        // Distinct rows cleaning down to one name are what the batch keys on; the unique index
+        // permits them, so two genre items can legitimately share a clean name.
+        var firstId = Guid.NewGuid();
+        var secondId = Guid.NewGuid();
+        var movieId = Guid.NewGuid();
+
+        using (var context = CreateDbContext())
+        {
+            foreach (var (id, name) in new[] { (firstId, "Sci-Fi"), (secondId, "SCI-FI") })
+            {
+                var genre = CreateItem(id);
+                genre.Type = "Genre";
+                genre.Name = name;
+                genre.CleanName = "sci-fi";
+                context.BaseItems.Add(genre);
+            }
+
+            var movie = CreateItem(movieId);
+            movie.Type = "Movie";
+            movie.IsFolder = false;
+            context.BaseItems.Add(movie);
+            context.SaveChanges();
+
+            foreach (var name in new[] { "Sci-Fi", "SCI-FI" })
+            {
+                var itemValue = new ItemValue
+                {
+                    ItemValueId = Guid.NewGuid(),
+                    Type = ItemValueType.Genre,
+                    Value = name,
+                    CleanValue = "sci-fi"
+                };
+                context.ItemValues.Add(itemValue);
+                context.SaveChanges();
+                Tag(context, movieId, itemValue.ItemValueId);
+            }
+
+            context.SaveChanges();
+        }
+
+        var filter = new InternalItemsQuery();
+        BaseItemKind[] related = [BaseItemKind.Movie];
+
+        var batch = _service.GetItemCountsForNameItems(BaseItemKind.Genre, [firstId, secondId], related, filter);
+
+        // One movie, reached through two value rows: counted once for each genre item, not twice.
+        Assert.Equal(1, batch[firstId].MovieCount);
+        Assert.Equal(1, batch[secondId].MovieCount);
+
+        foreach (var genreId in new[] { firstId, secondId })
+        {
+            var single = _service.GetItemCountsForNameItem(BaseItemKind.Genre, genreId, related, filter);
+            Assert.Equal(single.MovieCount, batch[genreId].MovieCount);
+        }
+    }
+
+    /// <summary>
+    /// Seeds three genres: one tagging a series whose episodes roll up (one of them tagged too)
+    /// plus a loose episode, one tagging only an episode of an untagged series, and one tagging
+    /// nothing.
+    /// </summary>
+    /// <returns>The ids of the seeded genres, in that order.</returns>
+    private List<Guid> SeedGenresTaggingSeriesAndEpisodes()
+    {
+        var genreIds = new List<Guid>();
+
+        using var context = CreateDbContext();
+
+        var values = new Dictionary<string, Guid>(StringComparer.Ordinal);
+        foreach (var name in new[] { "rolled", "loose", "empty" })
+        {
+            var genreId = Guid.NewGuid();
+            genreIds.Add(genreId);
+
+            var genre = CreateItem(genreId);
+            genre.Type = "Genre";
+            genre.Name = name;
+            genre.CleanName = name;
+            context.BaseItems.Add(genre);
+
+            var itemValue = new ItemValue
+            {
+                ItemValueId = Guid.NewGuid(),
+                Type = ItemValueType.Genre,
+                Value = name,
+                CleanValue = name
+            };
+            context.ItemValues.Add(itemValue);
+            values[name] = itemValue.ItemValueId;
+        }
+
+        context.SaveChanges();
+
+        // A series tagged "rolled" holding two episodes; the second carries "rolled" itself, so the
+        // roll-up and the direct tag both see it.
+        var taggedSeriesId = Guid.NewGuid();
+        var taggedSeries = CreateItem(taggedSeriesId);
+        taggedSeries.Type = "Series";
+        context.BaseItems.Add(taggedSeries);
+
+        var episodeOfTaggedSeries = CreateEpisode(Guid.NewGuid(), taggedSeriesId);
+        var taggedEpisodeOfTaggedSeries = CreateEpisode(Guid.NewGuid(), taggedSeriesId);
+        context.BaseItems.AddRange(episodeOfTaggedSeries, taggedEpisodeOfTaggedSeries);
+
+        // An untagged series whose episode carries a genre on its own.
+        var untaggedSeriesId = Guid.NewGuid();
+        var untaggedSeries = CreateItem(untaggedSeriesId);
+        untaggedSeries.Type = "Series";
+        context.BaseItems.Add(untaggedSeries);
+
+        var looseEpisode = CreateEpisode(Guid.NewGuid(), untaggedSeriesId);
+        var rolledLooseEpisode = CreateEpisode(Guid.NewGuid(), untaggedSeriesId);
+        context.BaseItems.AddRange(looseEpisode, rolledLooseEpisode);
+
+        var movieId = Guid.NewGuid();
+        var movie = CreateItem(movieId);
+        movie.Type = "Movie";
+        movie.IsFolder = false;
+        context.BaseItems.Add(movie);
+
+        context.SaveChanges();
+
+        Tag(context, taggedSeriesId, values["rolled"]);
+        Tag(context, taggedEpisodeOfTaggedSeries.Id, values["rolled"]);
+        Tag(context, rolledLooseEpisode.Id, values["rolled"]);
+        Tag(context, looseEpisode.Id, values["loose"]);
+        Tag(context, movieId, values["rolled"]);
+
+        context.SaveChanges();
+
+        return genreIds;
+    }
+
+    private static void Tag(JellyfinDbContext context, Guid itemId, Guid itemValueId)
+    {
+        context.ItemValuesMap.Add(new ItemValueMap
+        {
+            ItemId = itemId,
+            ItemValueId = itemValueId,
+            Item = null!,
+            ItemValue = null!
+        });
+    }
+
+    private static BaseItemEntity CreateEpisode(Guid id, Guid seriesId)
+    {
+        return new BaseItemEntity
+        {
+            Id = id,
+            Type = "Episode",
+            IsFolder = false,
+            IsVirtualItem = false,
+            ParentId = seriesId,
+            SeriesId = seriesId
+        };
+    }
+
     /// <summary>
     /// Seeds four genres tagging three, two, one and no movies, in that order.
     /// </summary>