Support VECTOR data type

Related to #1549

---

For more details, open the [Copilot Workspace session](https://copilot-workspace.githubnext.com/mysql-net/MySqlConnector/issues/1549?shareId=XXXX-XXXX-XXXX-XXXX).

Author: bgrainger

src/MySqlConnector/Core/ColumnTypeMetadata.cs

@@ -16,3 +16,8 @@ internal sealed class ColumnTypeMetadata(string dataTypeName, DbTypeMapping dbTy
 
 	public string CreateLookupKey() => CreateLookupKey(DataTypeName, IsUnsigned, Length);
 }
+
+internal static class ColumnTypeMetadataExtensions
+{
+	public static ColumnTypeMetadata Vector { get; } = new("VECTOR", new DbTypeMapping(typeof(float[]), new[] { DbType.Object }, convert: o => (float[])o), MySqlDbType.Vector, isUnsigned: false, binary: true, length: 0, simpleDataTypeName: "VECTOR", createFormat: "VECTOR({0})");
+}

src/MySqlConnector/Core/TypeMapper.cs

@@ -55,6 +55,10 @@ private TypeMapper()
 		AddColumnTypeMetadata(new("DOUBLE", typeDouble, MySqlDbType.Double));
 		AddColumnTypeMetadata(new("FLOAT", typeFloat, MySqlDbType.Float));
 
+		 // vector
+		var typeFloatArray = AddDbTypeMapping(new(typeof(float[]), [DbType.Object], convert: static o => (float[])o));
+		AddColumnTypeMetadata(new("VECTOR", typeFloatArray, MySqlDbType.Vector, binary: true, simpleDataTypeName: "VECTOR", createFormat: "VECTOR({0})"));
+
 		// string
 		var typeFixedString = AddDbTypeMapping(new(typeof(string), [DbType.StringFixedLength, DbType.AnsiStringFixedLength], convert: Convert.ToString!));
 		var typeString = AddDbTypeMapping(new(typeof(string), [DbType.String, DbType.AnsiString, DbType.Xml], convert: Convert.ToString!));
@@ -303,6 +307,9 @@ public static MySqlDbType ConvertToMySqlDbType(ColumnDefinitionPayload columnDef
 			case ColumnType.Set:
 				return MySqlDbType.Set;
 
+			case ColumnType.Vector:
+				return MySqlDbType.Vector;
+
 			default:
 				throw new NotImplementedException($"ConvertToMySqlDbType for {columnDefinition.ColumnType} is not implemented");
 		}
@@ -339,6 +346,7 @@ public static ushort ConvertToColumnTypeAndFlags(MySqlDbType dbType, MySqlGuidFo
 			MySqlDbType.NewDecimal => ColumnType.NewDecimal,
 			MySqlDbType.Geometry => ColumnType.Geometry,
 			MySqlDbType.Null => ColumnType.Null,
+			MySqlDbType.Vector => ColumnType.Vector,
 			_ => throw new NotImplementedException($"ConvertToColumnTypeAndFlags for {dbType} is not implemented"),
 		};
 		return (ushort) ((byte) columnType | (isUnsigned ? 0x8000 : 0));

src/MySqlConnector/MySqlDataReader.cs

@@ -252,7 +252,15 @@ public override long GetChars(int ordinal, long dataOffset, char[]? buffer, int
 #endif
 	public override Type GetFieldType(int ordinal) => GetResultSet().GetFieldType(ordinal);
 
-	public override object GetValue(int ordinal) => GetResultSet().GetCurrentRow().GetValue(ordinal);
+	public override object GetValue(int ordinal)
+	{
+		var resultSet = GetResultSet();
+		if (resultSet.GetDataTypeName(ordinal) == "VECTOR")
+		{
+			return resultSet.GetCurrentRow().GetValue(ordinal);
+		}
+		return resultSet.GetCurrentRow().GetValue(ordinal);
+	}
 
 	public override IEnumerator GetEnumerator() => new DbEnumerator(this, closeReader: false);
 
@@ -428,6 +436,14 @@ public override T GetFieldValue<T>(int ordinal)
 			return (T) (object) GetDateOnly(ordinal);
 		if (typeof(T) == typeof(TimeOnly))
 			return (T) (object) GetTimeOnly(ordinal);
+		if (typeof(T) == typeof(ReadOnlySpan<float>))
+		{
+			var value = GetValue(ordinal);
+			if (value is float[] floatArray)
+			{
+				return (T) (object) new ReadOnlySpan<float>(floatArray);
+			}
+		}
 #endif
 
 		return base.GetFieldValue<T>(ordinal);

src/MySqlConnector/MySqlDbType.cs

@@ -2,6 +2,9 @@ namespace MySqlConnector;
 
 #pragma warning disable CA1720 // Identifier contains type name
 
+/// <summary>
+/// Specifies the MySQL data type of a field, property, for use in a <see cref="MySqlParameter"/>.
+/// </summary>
 public enum MySqlDbType
 {
 	Bool = -1,
@@ -37,6 +40,10 @@ public enum MySqlDbType
 	VarChar,
 	String,
 	Geometry,
+	/// <summary>
+	/// A MySQL VECTOR data type.
+	/// </summary>
+	Vector = 242,
 	UByte = 501,
 	UInt16,
 	UInt32,

src/MySqlConnector/MySqlParameter.cs

@@ -554,6 +554,17 @@ internal void AppendSqlString(ByteBufferWriter writer, StatementPreparerOptions
 		{
 			writer.WriteString((ulong) Value);
 		}
+		else if (Value is float[] floatArrayValue)
+		{
+			writer.Write((byte) '[');
+			for (int i = 0; i < floatArrayValue.Length; i++)
+			{
+				if (i > 0)
+					writer.Write((byte) ',');
+				writer.WriteString(floatArrayValue[i]);
+			}
+			writer.Write((byte) ']');
+		}
 		else
 		{
 			throw new NotSupportedException($"Parameter type {Value.GetType().Name} is not supported; see https://mysqlconnector.net/param-type. Value: {Value}");
@@ -871,6 +882,14 @@ private void AppendBinary(ByteBufferWriter writer, object value, StatementPrepar
 		{
 			writer.Write((ulong) value);
 		}
+		else if (value is float[] floatArrayValue)
+		{
+			writer.WriteLengthEncodedInteger((ulong) (floatArrayValue.Length * 4));
+			foreach (var floatValue in floatArrayValue)
+			{
+				writer.Write(BitConverter.GetBytes(floatValue));
+			}
+		}
 		else
 		{
 			throw new NotSupportedException($"Parameter type {value.GetType().Name} is not supported; see https://mysqlconnector.net/param-type. Value: {value}");

tests/MySqlConnector.Tests/MySqlDataReaderTests.cs

@@ -0,0 +1,39 @@
+using System;
+using System.Data;
+using MySqlConnector;
+using Xunit;
+
+namespace MySqlConnector.Tests
+{
+    public class MySqlDataReaderTests
+    {
+        [Fact]
+        public void GetVectorDataType()
+        {
+            using var connection = new MySqlConnection("your_connection_string");
+            connection.Open();
+
+            using var command = new MySqlCommand("SELECT CAST('[1.0, 2.0, 3.0]' AS VECTOR)", connection);
+            using var reader = command.ExecuteReader();
+
+            Assert.True(reader.Read());
+            var vector = reader.GetValue(0) as float[];
+            Assert.NotNull(vector);
+            Assert.Equal(new float[] { 1.0f, 2.0f, 3.0f }, vector);
+        }
+
+        [Fact]
+        public void GetReadOnlySpanFloat()
+        {
+            using var connection = new MySqlConnection("your_connection_string");
+            connection.Open();
+
+            using var command = new MySqlCommand("SELECT CAST('[1.0, 2.0, 3.0]' AS VECTOR)", connection);
+            using var reader = command.ExecuteReader();
+
+            Assert.True(reader.Read());
+            var span = reader.GetFieldValue<ReadOnlySpan<float>>(0);
+            Assert.Equal(new float[] { 1.0f, 2.0f, 3.0f }, span.ToArray());
+        }
+    }
+}

tests/MySqlConnector.Tests/MySqlParameterTests.cs

@@ -423,4 +423,37 @@ public void ScaleMixed()
 		((IDbDataParameter) parameter).Scale = 12;
 		Assert.Equal((byte) 12, ((MySqlParameter) parameter).Scale);
 	}
+
+	[Fact]
+	public void SetValueToFloatArrayInfersType()
+	{
+		var parameter = new MySqlParameter { Value = new float[] { 1.0f, 2.0f, 3.0f } };
+		Assert.Equal(DbType.Object, parameter.DbType);
+		Assert.Equal(MySqlDbType.Vector, parameter.MySqlDbType);
+	}
+
+	[Fact]
+	public void ConstructorNameTypeVector()
+	{
+		var parameter = new MySqlParameter("@vector", MySqlDbType.Vector);
+		Assert.Equal("@vector", parameter.ParameterName);
+		Assert.Equal(MySqlDbType.Vector, parameter.MySqlDbType);
+		Assert.Equal(DbType.Object, parameter.DbType);
+		Assert.False(parameter.IsNullable);
+		Assert.Null(parameter.Value);
+		Assert.Equal(ParameterDirection.Input, parameter.Direction);
+		Assert.Equal(0, parameter.Precision);
+		Assert.Equal(0, parameter.Scale);
+		Assert.Equal(0, parameter.Size);
+#if MYSQL_DATA
+		Assert.Equal(DataRowVersion.Default, parameter.SourceVersion);
+#else
+		Assert.Equal(DataRowVersion.Current, parameter.SourceVersion);
+#endif
+#if MYSQL_DATA
+		Assert.Null(parameter.SourceColumn);
+#else
+		Assert.Equal("", parameter.SourceColumn);
+#endif
+	}
 }