Allow random queries to be paginated

back/src/Kyoo.Postgresql/DatabaseContext.cs

@@ -41,6 +41,13 @@ namespace Kyoo.Postgresql
 	/// </remarks>
 	public abstract class DatabaseContext : DbContext
 	{
+		/// <summary>
+		/// Calculate the MD5 of a string, can only be used in database context.
+		/// </summary>
+		/// <param name="str">The string to hash</param>
+		/// <returns>The hash</returns>
+		public static string MD5(string str) => throw new NotSupportedException();
+
 		/// <summary>
 		/// All collections of Kyoo. See <see cref="Collection"/>.
 		/// </summary>

back/src/Kyoo.Postgresql/Kyoo.Postgresql.csproj

@@ -2,6 +2,7 @@
 	<PropertyGroup>
 		<AssemblyName>Kyoo.Postgresql</AssemblyName>
 		<RootNamespace>Kyoo.Postgresql</RootNamespace>
+		<Nullable>enable</Nullable>
 	</PropertyGroup>
 
 	<ItemGroup>

back/src/Kyoo.Postgresql/PostgresContext.cs

@@ -18,12 +18,14 @@
 
 using System;
 using System.Globalization;
+using System.Linq;
 using System.Linq.Expressions;
 using System.Reflection;
 using EFCore.NamingConventions.Internal;
 using Kyoo.Abstractions.Models;
 using Kyoo.Utils;
 using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Query.SqlExpressions;
 using Npgsql;
 
 namespace Kyoo.Postgresql
@@ -104,6 +106,18 @@ namespace Kyoo.Postgresql
 			modelBuilder.HasPostgresEnum<Genre>();
 			modelBuilder.HasPostgresEnum<ItemKind>();
 
+			modelBuilder.HasDbFunction(typeof(DatabaseContext).GetMethod(nameof(MD5)))
+				.HasTranslation(args =>
+					new SqlFunctionExpression(
+						"md5",
+						args,
+						nullable: true,
+						argumentsPropagateNullability: new[] { false },
+						type: args[0].Type,
+						typeMapping: args[0].TypeMapping
+					)
+				);
+
 			base.OnModelCreating(modelBuilder);
 		}