Add NpgsqlPgLsnTypeMapping to map the pg_lsn internal type (#2165)

src/EFCore.PG/Storage/Internal/Mapping/NpgsqlPgLsnTypeMapping.cs

@@ -0,0 +1,43 @@
+using NpgsqlTypes;
+using System.Text;
+
+namespace Npgsql.EntityFrameworkCore.PostgreSQL.Storage.Internal.Mapping;
+
+/// <summary>
+/// The type mapping for the PostgreSQL pg_lsn type.
+/// </summary>
+/// <remarks>
+/// See: https://www.postgresql.org/docs/current/datatype-pg-lsn.html
+/// </remarks>
+public class NpgsqlPgLsnTypeMapping : NpgsqlTypeMapping
+{
+    /// <summary>
+    /// Initializes  a new instance of the <see cref="NpgsqlPgLsnTypeMapping"/> class.
+    /// </summary>
+    public NpgsqlPgLsnTypeMapping()
+        : base("pg_lsn", typeof(NpgsqlLogSequenceNumber), NpgsqlDbType.PgLsn) {}
+
+    protected NpgsqlPgLsnTypeMapping(RelationalTypeMappingParameters parameters)
+        : base(parameters, NpgsqlDbType.PgLsn) {}
+
+    protected override RelationalTypeMapping Clone(RelationalTypeMappingParameters parameters)
+        => new NpgsqlPgLsnTypeMapping(parameters);
+
+    protected override string GenerateNonNullSqlLiteral(object value)
+    {
+        var lsn = (NpgsqlLogSequenceNumber)value;
+        var builder = new StringBuilder("PG_LSN '")
+                .Append(lsn.ToString())
+                .Append('\'');
+        return builder.ToString();
+    }
+
+    public override Expression GenerateCodeLiteral(object value)
+    {
+        var lsn = (NpgsqlLogSequenceNumber)value;
+        return Expression.New(Constructor, Expression.Constant((ulong)lsn));
+    }
+
+    private static readonly ConstructorInfo Constructor =
+        typeof(NpgsqlLogSequenceNumber).GetConstructor(new[] { typeof(ulong) })!;
+}

src/EFCore.PG/Storage/Internal/NpgsqlTypeMappingSource.cs

@@ -161,6 +161,7 @@ static NpgsqlTypeMappingSource()
     private readonly NpgsqlHstoreTypeMapping          _hstore          = new(typeof(Dictionary<string, string>));
     private readonly NpgsqlHstoreTypeMapping          _immutableHstore = new(typeof(ImmutableDictionary<string, string>));
     private readonly NpgsqlTidTypeMapping             _tid             = new();
+    private readonly NpgsqlPgLsnTypeMapping           _pgLsn           = new();
 
     private readonly NpgsqlLTreeTypeMapping           _ltree           = new();
     private readonly NpgsqlStringTypeMapping          _ltreeString     = new("ltree", NpgsqlDbType.LTree);
@@ -296,6 +297,7 @@ public NpgsqlTypeMappingSource(TypeMappingSourceDependencies dependencies,
             { "regtype",                     new[] { _regtype                      } },
             { "lo",                          new[] { _lo                           } },
             { "tid",                         new[] { _tid                          } },
+            { "pg_lsn",                      new[] { _pgLsn                        } },
 
             { "int4range",                   new[] { _int4range                    } },
             { "int8range",                   new[] { _int8range                    } },
@@ -363,6 +365,7 @@ public NpgsqlTypeMappingSource(TypeMappingSourceDependencies dependencies,
             { typeof(ImmutableDictionary<string, string>), _immutableHstore      },
             { typeof(Dictionary<string, string>),          _hstore               },
             { typeof(NpgsqlTid),                           _tid                  },
+            { typeof(NpgsqlLogSequenceNumber),             _pgLsn                },
 
             { typeof(NpgsqlPoint),                         _point                },
             { typeof(NpgsqlBox),                           _box                  },

test/EFCore.PG.Tests/Storage/NpgsqlTypeMappingTest.cs

@@ -455,6 +455,10 @@ private enum DummyEnum
     public void GenerateSqlLiteral_returns_tid_literal()
         => Assert.Equal(@"TID '(0,1)'", GetMapping("tid").GenerateSqlLiteral(new NpgsqlTid(0, 1)));
 
+    [Fact]
+    public void GenerateSqlLiteral_returns_pg_lsn_literal()
+        => Assert.Equal(@"PG_LSN '12345/67890'", GetMapping("pg_lsn").GenerateSqlLiteral(NpgsqlLogSequenceNumber.Parse("12345/67890")));
+
     #endregion Misc
 
     #region Array