diff --git a/back/src/Kyoo.Core/Controllers/Repositories/LibraryItemRepository.cs b/back/src/Kyoo.Core/Controllers/Repositories/LibraryItemRepository.cs
index 25500bf2..96a885f8 100644
--- a/back/src/Kyoo.Core/Controllers/Repositories/LibraryItemRepository.cs
+++ b/back/src/Kyoo.Core/Controllers/Repositories/LibraryItemRepository.cs
@@ -20,7 +20,6 @@ using System;
 using System.Collections.Generic;
 using System.Data.Common;
 using System.IO;
-using System.Linq.Expressions;
 using System.Threading.Tasks;
 using Kyoo.Abstractions.Controllers;
 using Kyoo.Abstractions.Models;
@@ -66,9 +65,15 @@ namespace Kyoo.Core.Controllers
 			if (items[0] is Show show && show.Id != 0)
 				return show;
 			if (items[1] is Movie movie && movie.Id != 0)
+			{
+				movie.Id = -movie.Id;
 				return movie;
+			}
 			if (items[2] is Collection collection && collection.Id != 0)
+			{
+				collection.Id += 10_000;
 				return collection;
+			}
 			throw new InvalidDataException();
 		}
 
@@ -77,27 +82,48 @@ namespace Kyoo.Core.Controllers
 		{ }
 
 		public async Task<ICollection<ILibraryItem>> GetAllOfCollection(
-			Expression<Func<Collection, bool>> selector,
-			Expression<Func<ILibraryItem, bool>>? where = null,
+			int collectionId,
+			Filter<ILibraryItem>? filter = default,
 			Sort<ILibraryItem>? sort = default,
-			Pagination? limit = default,
-			Include<ILibraryItem>? include = default)
+			Include<ILibraryItem>? include = default,
+			Pagination? limit = default)
 		{
-			throw new NotImplementedException();
-			// return await ApplyFilters(
-			// 	_database.LibraryItems
-			// 		.Where(item =>
-			// 			_database.Movies
-			// 				.Where(x => x.Id == -item.Id)
-			// 				.Any(x => x.Collections!.AsQueryable().Any(selector))
-			// 			|| _database.Shows
-			// 				.Where(x => x.Id == item.Id)
-			// 				.Any(x => x.Collections!.AsQueryable().Any(selector))
-			// 		),
-			// 	where,
-			// 	sort,
-			// 	limit,
-			// 	include);
+			// language=PostgreSQL
+			FormattableString sql = $"""
+				select
+					s.*,
+					m.*
+					/* includes */
+				from (
+					select
+						* -- Show
+					from
+						shows
+					inner join link_collection_show as ls on ls.show_id = id and ls.collection_id = {collectionId}
+				) as s
+				full outer join (
+					select
+						* -- Movie
+					from
+						movies
+					inner join link_collection_movie as lm on lm.movie_id = id and lm.collection_id = {collectionId}
+				) as m on false
+			""";
+
+			return await Database.Query<ILibraryItem>(
+				sql,
+				new()
+				{
+					{ "s", typeof(Show) },
+					{ "m", typeof(Movie) },
+				},
+				Mapper,
+				(id) => Get(id),
+				include,
+				filter,
+				sort ?? new Sort<ILibraryItem>.Default(),
+				limit ?? new()
+			);
 		}
 	}
 }
diff --git a/back/src/Kyoo.Core/Views/Resources/CollectionApi.cs b/back/src/Kyoo.Core/Views/Resources/CollectionApi.cs
index e8d3d285..74f6255f 100644
--- a/back/src/Kyoo.Core/Views/Resources/CollectionApi.cs
+++ b/back/src/Kyoo.Core/Views/Resources/CollectionApi.cs
@@ -144,17 +144,21 @@ namespace Kyoo.Core.Api
 			[FromQuery] Pagination pagination,
 			[FromQuery] Include<ILibraryItem>? fields)
 		{
-			// ICollection<ILibraryItem> resources = await _items.GetAllOfCollection(
-			// 	identifier.IsSame<Collection>(),
-			// 	filter,
-			// 	sortBy == new Sort<ILibraryItem>.Default() ? new Sort<ILibraryItem>.By(nameof(Movie.AirDate)) : sortBy,
-			// 	pagination,
-			// 	fields
-			// );
+			int collectionId = await identifier.Match(
+				id => Task.FromResult(id),
+				async slug => (await _libraryManager.Collections.Get(slug)).Id
+			);
+			ICollection<ILibraryItem> resources = await _items.GetAllOfCollection(
+				collectionId,
+				filter,
+				sortBy == new Sort<ILibraryItem>.Default() ? new Sort<ILibraryItem>.By(nameof(Movie.AirDate)) : sortBy,
+				fields,
+				pagination
+			);
 
-			// if (!resources.Any() && await _libraryManager.Collections.GetOrDefault(identifier.IsSame<Collection>()) == null)
+			if (!resources.Any() && await _libraryManager.Collections.GetOrDefault(identifier.IsSame<Collection>()) == null)
 				return NotFound();
-			// return Page(resources, pagination.Limit);
+			return Page(resources, pagination.Limit);
 		}
 
 		/// <summary>
diff --git a/back/src/Kyoo.Meilisearch/SearchManager.cs b/back/src/Kyoo.Meilisearch/SearchManager.cs
index f88f369d..dc49cb5e 100644
--- a/back/src/Kyoo.Meilisearch/SearchManager.cs
+++ b/back/src/Kyoo.Meilisearch/SearchManager.cs
@@ -88,7 +88,7 @@ public class SearchManager : ISearchManager
 		});
 
 		// Since library items's ID are still ints mapped from real items ids, we must map it here to match the db's value.
-		// Look at the items Migration's sql to understand where magic numbers come from.
+		// Look at the LibraryItemRepository's Mapper to understand what those magic numbers are.
 		List<int> ids = res.Hits.Select(x => x.Kind switch
 		{
 			nameof(Show) => x.Id,