Fix LTree type mapping (#1930)

Allow mapping string to PG ltree, not just the .NET LTree type (which
is supported via value conversion, as the ADO layer only supports
string). This also resolves issues in seeding.

Fixes #1929

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

@@ -0,0 +1,36 @@
+using System.Linq.Expressions;
+using System.Reflection;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Storage;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+using NpgsqlTypes;
+
+namespace Npgsql.EntityFrameworkCore.PostgreSQL.Storage.Internal.Mapping
+{
+    public class NpgsqlLTreeTypeMapping : NpgsqlStringTypeMapping
+    {
+        private static readonly ConstructorInfo Constructor = typeof(LTree).GetConstructor(new[] { typeof(string) })!;
+
+        public NpgsqlLTreeTypeMapping()
+            : base(
+                new RelationalTypeMappingParameters(
+                    new CoreTypeMappingParameters(
+                        typeof(LTree),
+                        new ValueConverter<LTree, string>(l => l, s => new(s))),
+                    "ltree"),
+                NpgsqlDbType.LTree)
+        {
+        }
+
+        protected NpgsqlLTreeTypeMapping(RelationalTypeMappingParameters parameters)
+            : base(parameters, NpgsqlDbType.LTree)
+        {
+        }
+
+        protected override RelationalTypeMapping Clone(RelationalTypeMappingParameters parameters)
+            => new NpgsqlLTreeTypeMapping(parameters);
+
+        public override Expression GenerateCodeLiteral(object value)
+            => Expression.New(Constructor, Expression.Constant((string)(LTree)value, typeof(string)));
+    }
+}

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

@@ -125,7 +125,8 @@ public class NpgsqlTypeMappingSource : RelationalTypeMappingSource
         private readonly NpgsqlHstoreTypeMapping          _immutableHstore = new(typeof(ImmutableDictionary<string, string>));
         private readonly NpgsqlTidTypeMapping             _tid             = new();
 
-        private readonly LTreeTypeMapping                 _ltree           = new();
+        private readonly NpgsqlLTreeTypeMapping           _ltree           = new();
+        private readonly NpgsqlStringTypeMapping          _ltreeString     = new("ltree", NpgsqlDbType.LTree);
         private readonly NpgsqlStringTypeMapping          _lquery          = new("lquery", NpgsqlDbType.LQuery);
         private readonly NpgsqlStringTypeMapping          _ltxtquery       = new("ltxtquery", NpgsqlDbType.LTxtQuery);
 
@@ -251,7 +252,7 @@ public NpgsqlTypeMappingSource(TypeMappingSourceDependencies dependencies,
                 { "tsvector",                    new[] { _tsvector                     } },
                 { "regconfig",                   new[] { _regconfig                    } },
 
-                { "ltree",                       new[] { _ltree                        } },
+                { "ltree",                       new[] { _ltree, _ltreeString          } },
                 { "lquery",                      new[] { _lquery                       } },
                 { "ltxtquery",                   new[] { _ltxtquery                    } },
 

test/EFCore.PG.FunctionalTests/Query/LTreeQueryTest.cs

@@ -1,4 +1,5 @@
 using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
 using System.Linq;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.EntityFrameworkCore.TestUtilities;
@@ -27,6 +28,7 @@ public void Load()
             using var ctx = CreateContext();
             var entity = ctx.LTreeEntities.Single(l => l.Id == 5);
             Assert.Equal("Top.Science.Astronomy.Cosmology", entity.Path);
+            Assert.Equal("Top.Science.Astronomy.Cosmology", entity.PathAsString);
         }
 
         [ConditionalFact]
@@ -58,6 +60,19 @@ SELECT COUNT(*)::INT
 WHERE l.""Path"" = @__p_0");
         }
 
+        [ConditionalFact]
+        public void Compare_string_to_string_literal()
+        {
+            using var ctx = CreateContext();
+            var count = ctx.LTreeEntities.Count(l => l.PathAsString == "Top.Science");
+
+            Assert.Equal(1, count);
+            AssertSql(
+                @"SELECT COUNT(*)::INT
+FROM ""LTreeEntities"" AS l
+WHERE l.""PathAsString"" = 'Top.Science'");
+        }
+
         [ConditionalFact]
         public void LTree_cast_to_string()
         {
@@ -105,7 +120,7 @@ public void LTree_matches_LQuery()
 
             Assert.Equal(4, entity.Id);
             AssertSql(
-                @"SELECT l.""Id"", l.""Path""
+                @"SELECT l.""Id"", l.""Path"", l.""PathAsString""
 FROM ""LTreeEntities"" AS l
 WHERE l.""Path"" ~ '*.Astrophysics'
 LIMIT 2");
@@ -122,7 +137,7 @@ public void LTree_matches_any_LQuery()
             AssertSql(
                 @"@__lqueries_0={ '*.Astrophysics', '*.Geology' } (DbType = Object)
 
-SELECT l.""Id"", l.""Path""
+SELECT l.""Id"", l.""Path"", l.""PathAsString""
 FROM ""LTreeEntities"" AS l
 WHERE l.""Path"" ? @__lqueries_0
 LIMIT 2");
@@ -149,7 +164,7 @@ public void LTree_concat()
 
             Assert.Equal(2, entity.Id);
             AssertSql(
-                @"SELECT l.""Id"", l.""Path""
+                @"SELECT l.""Id"", l.""Path"", l.""PathAsString""
 FROM ""LTreeEntities"" AS l
 WHERE (CAST(l.""Path"" AS text) || '.Astronomy') = 'Top.Science.Astronomy'
 LIMIT 2");
@@ -342,7 +357,7 @@ public void Subpath2()
 
             Assert.Equal(4, result.Id);
             AssertSql(
-                @"SELECT l.""Id"", l.""Path""
+                @"SELECT l.""Id"", l.""Path"", l.""PathAsString""
 FROM ""LTreeEntities"" AS l
 WHERE (nlevel(l.""Path"") > 2) AND (subpath(l.""Path"", 2) = 'Astronomy.Astrophysics')
 LIMIT 2");
@@ -422,14 +437,23 @@ protected override void OnModelCreating(ModelBuilder modelBuilder)
 
             public static void Seed(LTreeQueryContext context)
             {
-                context.LTreeEntities.AddRange(
-                    new LTreeEntity { Id = 1, Path = "Top" },
-                    new LTreeEntity { Id = 2, Path = "Top.Science" },
-                    new LTreeEntity { Id = 3, Path = "Top.Science.Astronomy" },
-                    new LTreeEntity { Id = 4, Path = "Top.Science.Astronomy.Astrophysics" },
-                    new LTreeEntity { Id = 5, Path = "Top.Science.Astronomy.Cosmology" },
-                    new LTreeEntity { Id = 6, Path = "Top.Hobbies" },
-                    new LTreeEntity { Id = 7, Path = "Top.Hobbies.Amateurs_Astronomy" });
+                var ltreeEntities = new LTreeEntity[]
+                {
+                    new() { Id = 1, Path = "Top" },
+                    new() { Id = 2, Path = "Top.Science" },
+                    new() { Id = 3, Path = "Top.Science.Astronomy" },
+                    new() { Id = 4, Path = "Top.Science.Astronomy.Astrophysics" },
+                    new() { Id = 5, Path = "Top.Science.Astronomy.Cosmology" },
+                    new() { Id = 6, Path = "Top.Hobbies" },
+                    new() { Id = 7, Path = "Top.Hobbies.Amateurs_Astronomy" }
+                };
+
+                foreach (var ltreeEntity in ltreeEntities)
+                {
+                    ltreeEntity.PathAsString = ltreeEntity.Path;
+                }
+
+                context.LTreeEntities.AddRange(ltreeEntities);
                 context.SaveChanges();
             }
         }
@@ -440,6 +464,10 @@ public class LTreeEntity
 
             [Required]
             public LTree Path { get; set; }
+
+            [Required]
+            [Column(TypeName = "ltree")]
+            public string PathAsString { get; set; }
         }
 
         public class LTreeQueryFixture : SharedStoreFixtureBase<LTreeQueryContext>