Npgsql: Demonstrate OBJECT type mapping using JsonDocument

CrateDB's OBJECT data type can also be communicated using .NET's native
`System.Text.Json.JsonDocument` type.

Author: amotl

by-language/csharp-npgsql/DemoProgram.cs

@@ -28,6 +28,8 @@ await Parser.Default.ParseArguments<Options>(args)
                     await DatabaseWorkloads.BasicConversationExample(conn);
                     await DatabaseWorkloads.UnnestExample(conn);
                     await DatabaseWorkloadsMore.AllTypesNativeExample(conn);
+                    await DatabaseWorkloadsMore.ObjectJsonDocumentExample(conn);
+                    // await DatabaseWorkloadsMore.ArrayJsonDocumentExample(conn);
                     await DatabaseWorkloadsMore.ObjectPocoExample(conn);
                     await DatabaseWorkloadsMore.ArrayPocoExample(conn);
                     conn.Close();

by-language/csharp-npgsql/DemoTypes.cs

@@ -1,9 +1,8 @@
 #nullable enable
 using System;
-using System.Collections;
 using System.Collections.Generic;
 using System.Data;
-using System.Reflection;
+using System.Text.Json;
 using System.Threading.Tasks;
 using Newtonsoft.Json;
 using Npgsql;
@@ -57,9 +56,9 @@ public class AllTypesRecord
     public class DatabaseWorkloadsMore
     {
 
-        public static async Task<DataTable> AllTypesNativeExample(NpgsqlConnection conn)
+        public static async Task ProvisionAllTypes(NpgsqlConnection conn)
         {
-            Console.WriteLine("Running AllTypesNativeExample");
+            Console.WriteLine("Running ProvisionAllTypes");
 
             // Submit DDL, create database schema.
             await using (var cmd = new NpgsqlCommand("DROP TABLE IF EXISTS testdrive.example", conn))
@@ -169,6 +168,15 @@ INSERT INTO testdrive.example (
                 cmd.ExecuteNonQuery();
             }
 
+        }
+
+        public static async Task<DataTable> AllTypesNativeExample(NpgsqlConnection conn)
+        {
+            Console.WriteLine("Running AllTypesNativeExample");
+
+            // Provision data.
+            await ProvisionAllTypes(conn);
+
             // Query back data.
             await using (var cmd = new NpgsqlCommand("SELECT * FROM testdrive.example", conn))
             await using (var reader = cmd.ExecuteReader())
@@ -182,6 +190,69 @@ INSERT INTO testdrive.example (
 
         }
 
+        public static async Task<JsonDocument> ObjectJsonDocumentExample(NpgsqlConnection conn)
+        {
+            Console.WriteLine("Running ObjectJsonDocumentExample");
+
+            // Provision data.
+            await ProvisionAllTypes(conn);
+
+            // This test uses the central DDL, but a blank slate to focus on the test case at hand.
+            await using (var cmd = new NpgsqlCommand("DELETE FROM testdrive.example", conn))
+            {
+                cmd.ExecuteNonQuery();
+            }
+
+            await using (var cmd = new NpgsqlCommand("""
+            INSERT INTO testdrive.example (
+              "object"
+            ) VALUES (
+              @object
+            )
+            """, conn))
+            {
+                cmd.Parameters.AddWithValue("object", NpgsqlDbType.Json, JsonDocument.Parse("""{"foo":"bar"}"""));
+                cmd.ExecuteNonQuery();
+            }
+
+            // Flush data.
+            await using (var cmd = new NpgsqlCommand("REFRESH TABLE testdrive.example", conn))
+            {
+                cmd.ExecuteNonQuery();
+            }
+
+            // Query back data.
+            await using (var cmd = new NpgsqlCommand("SELECT * FROM testdrive.example", conn))
+            await using (var reader = cmd.ExecuteReader())
+            {
+                reader.Read();
+                var obj = reader.GetFieldValue<JsonDocument>("object");
+                Console.WriteLine(obj);
+                return obj;
+            }
+        }
+
+        public static async Task<List<JsonDocument>> ArrayJsonDocumentExample(NpgsqlConnection conn)
+        {
+            Console.WriteLine("Running ArrayJsonDocumentExample");
+
+            // Provision data.
+            await ProvisionAllTypes(conn);
+
+            // Query back data.
+            await using (var cmd = new NpgsqlCommand("SELECT * FROM testdrive.example", conn))
+            await using (var reader = cmd.ExecuteReader())
+            {
+                reader.Read();
+                // TODO: System.InvalidCastException: Reading as 'System.Text.Json.JsonDocument' or [1]
+                //       is not supported for fields having DataTypeName 'character varying[]'.
+                //       [1] `System.Collections.Generic.List`1[[System.Text.Json.JsonDocument]`
+                var obj = reader.GetFieldValue<List<JsonDocument>>("array");
+                Console.WriteLine(obj);
+                return obj;
+            }
+        }
+
         public static async Task ProvisionPoco(NpgsqlConnection conn)
         {
             /***

by-language/csharp-npgsql/tests/DemoProgramTest.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Data;
 using System.Linq;
+using System.Text.Json;
 using System.Threading.Tasks;
 using Npgsql;
 using Xunit;
@@ -168,6 +169,19 @@ public async Task TestContainerTypesExample()
 
         }
 
+        [Fact]
+        public async Task TestObjectJsonDocumentExample()
+        {
+            var conn = fixture.Db;
+
+            // Invoke database workload.
+            var task = DatabaseWorkloadsMore.ObjectJsonDocumentExample(conn);
+            var obj = await task.WaitAsync(TimeSpan.FromSeconds(0.5));
+
+            // Validate the outcome.
+            Assert.Equal("""{"foo":"bar"}""", JsonSerializer.Serialize(obj));
+        }
+
         [Fact]
         public async Task TestObjectPocoExample()
         {