Add float16 vector backward compatibility tests and refactor float32 vectors as varchar(max) test suite.

src/Microsoft.Data.SqlClient/tests/ManualTests/DataCommon/DataTestUtility.cs

@@ -95,6 +95,7 @@ public static class DataTestUtility
         // SQL Server capabilities
         private static bool? s_isDataClassificationSupported;
         private static bool? s_isVectorSupported;
+        private static bool? s_isVectorFloat16Supported;
 
         // Azure Synapse EngineEditionId == 6
         // More could be read at https://learn.microsoft.com/en-us/sql/t-sql/functions/serverproperty-transact-sql?view=sql-server-ver16#propertyname
@@ -156,6 +157,68 @@ public static string SQLServerVersion
             s_isVectorSupported ??= IsTCPConnStringSetup() &&
                 IsTypePresent("vector");
 
+        /// <summary>
+        /// Determines whether the SQL Server supports the 'float16' base type for the 'vector' data type.
+        /// </summary>
+        /// <remarks>
+        /// Probes the server by first executing
+        /// <c>ALTER DATABASE SCOPED CONFIGURATION SET PREVIEW_FEATURES = ON;</c> and then executing
+        /// <c>DECLARE @v AS VECTOR(5, float16) = '[1.0, 1.0, 1.0, 1.0, 1.0]'; SELECT @v;</c>.
+        /// As a side effect, this enables preview features for the current database. If the server does not
+        /// recognize <c>float16</c> as a vector base type, if the server does not support the required syntax,
+        /// if the current principal lacks permission to change the database scoped configuration, or if another
+        /// server-side error occurs while running the probe, this method returns
+        /// <see langword="false"/>. Implies <see cref="IsSqlVectorSupported"/>.
+        /// </remarks>
+        /// <returns><see langword="true"/> if the 'float16' vector base type is supported; otherwise, <see langword="false"/>.</returns>
+        public static bool IsSqlVectorFloat16Supported =>
+            s_isVectorFloat16Supported ??= IsTCPConnStringSetup() &&
+                IsSqlVectorSupported &&
+                CheckVectorFloat16Supported();
+
+        private static bool CheckVectorFloat16Supported()
+        {
+            try
+            {
+                using SqlConnection connection = new(TCPConnectionString);
+                // Enable preview features (required while float16 is in preview), then declare a
+                // float16 vector and select it back. Without a negotiated float16 feature extension,
+                // the server returns the value as a varchar(max) JSON string, which the client can
+                // safely read. We use 1.0 (exactly representable in IEEE-754 binary16) so the
+                // round-tripped JSON matches the input bit-for-bit. Any failure (server parse
+                // error such as Msg 195 "'float16' is not a recognized vector base type.", lack of
+                // permission to set PREVIEW_FEATURES, etc.) means we cannot exercise the float16
+                // path.
+                float[] expected = { 1.0f, 1.0f, 1.0f, 1.0f, 1.0f };
+                using SqlCommand command = new(
+                    "ALTER DATABASE SCOPED CONFIGURATION SET PREVIEW_FEATURES = ON;" +
+                    "DECLARE @v AS VECTOR(5, float16) = '[1.0, 1.0, 1.0, 1.0, 1.0]'; SELECT @v;",
+                    connection);
+                connection.Open();
+                using SqlDataReader reader = command.ExecuteReader();
+                if (!reader.Read())
+                {
+                    return false;
+                }
+                string json = reader.GetString(0);
+                float[] actual = System.Text.Json.JsonSerializer.Deserialize<float[]>(json);
+                return actual != null && actual.Length == expected.Length
+                    && actual.AsSpan().SequenceEqual(expected);
+            }
+            catch (SqlException)
+            {
+                // Server-side failure (e.g. Msg 195 "'float16' is not a recognized vector base
+                // type.", Msg 102 syntax errors on older servers, lack of permission to set
+                // PREVIEW_FEATURES) — float16 path is unavailable.
+                return false;
+            }
+            catch (System.Text.Json.JsonException)
+            {
+                // Server returned a payload we can't parse as a float[] JSON array.
+                return false;
+            }
+        }
+
         static DataTestUtility()
         {
             Config c = Config.Load();

src/Microsoft.Data.SqlClient/tests/ManualTests/Microsoft.Data.SqlClient.ManualTests.csproj

@@ -243,8 +243,10 @@
     <Compile Include="SQL\UdtTest\UdtTest2.cs" />
     <Compile Include="SQL\UdtTest\UdtTestHelpers.cs" />
     <Compile Include="SQL\Utf8SupportTest\Utf8SupportTest.cs" />
+    <Compile Include="SQL\VectorTest\Float16VectorTypeBackwardCompatibilityTests.cs" />
     <Compile Include="SQL\VectorTest\NativeVectorFloat32Tests.cs" />
     <Compile Include="SQL\VectorTest\VectorAPIValidationTest.cs" />
+    <Compile Include="SQL\VectorTest\VectorBackwardCompatTestBase.cs" />
     <Compile Include="SQL\VectorTest\VectorTypeBackwardCompatibilityTests.cs" />
     <Compile Include="SQL\WeakRefTest\WeakRefTest.cs" />
     <Compile Include="SQL\WeakRefTestYukonSpecific\WeakRefTestYukonSpecific.cs" />

src/Microsoft.Data.SqlClient/tests/ManualTests/SQL/VectorTest/Float16VectorTypeBackwardCompatibilityTests.cs

@@ -0,0 +1,106 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Text.Json;
+using System.Threading.Tasks;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace Microsoft.Data.SqlClient.ManualTesting.Tests.SQL.VectorTest
+{
+    /// <summary>
+    /// Provides parameterized test data for backward compatibility tests that exchange
+    /// float16 vector data as varchar(max) JSON strings.
+    /// </summary>
+    public static class Float16VarcharVectorTestData
+    {
+        // Values chosen to be exactly representable in IEEE-754 binary16 (float16),
+        // so JSON round-trips through a vector(N, float16) column without precision loss.
+        public static readonly float[] TestData = { 1.0f, 2.0f, 3.0f };
+
+        /// <summary>
+        /// Generates test cases for all 4 SqlParameter construction patterns x 2 value types (non-null + null).
+        /// Each case yields: [int pattern, string jsonOrNull, float[] expectedData]
+        /// where jsonOrNull is null when testing DBNull insertion.
+        /// </summary>
+        public static IEnumerable<object[]> GetVarcharVectorInsertTestData()
+        {
+            string json = JsonSerializer.Serialize(TestData);
+
+            // Pattern 1-4 with non-null JSON value
+            yield return new object[] { 1, json, TestData };
+            yield return new object[] { 2, json, TestData };
+            yield return new object[] { 3, json, TestData };
+            yield return new object[] { 4, json, TestData };
+
+            // Pattern 1-4 with null value
+            yield return new object[] { 1, null, null };
+            yield return new object[] { 2, null, null };
+            yield return new object[] { 3, null, null };
+            yield return new object[] { 4, null, null };
+        }
+    }
+
+    public sealed class Float16VectorTypeBackwardCompatibilityTests : VectorBackwardCompatTestBase
+    {
+        public Float16VectorTypeBackwardCompatibilityTests(ITestOutputHelper output)
+            : base(output, columnDefinition: "vector(3, float16)", namePrefix: "VectorF16")
+        {
+        }
+
+        protected override float[] GetPrepareTestValues(int i) =>
+            new float[] { i + 1, i + 2, i + 3 };
+
+        #region Insert Tests
+
+        [ConditionalTheory(typeof(DataTestUtility), nameof(DataTestUtility.AreConnStringsSetup), nameof(DataTestUtility.IsSqlVectorFloat16Supported))]
+        [MemberData(nameof(Float16VarcharVectorTestData.GetVarcharVectorInsertTestData), MemberType = typeof(Float16VarcharVectorTestData), DisableDiscoveryEnumeration = true)]
+        public void TestVectorDataInsertionAsVarchar(int pattern, string jsonValue, float[] expectedData)
+            => InsertAndValidateAsVarchar(pattern, jsonValue, expectedData);
+
+        [ConditionalTheory(typeof(DataTestUtility), nameof(DataTestUtility.AreConnStringsSetup), nameof(DataTestUtility.IsSqlVectorFloat16Supported))]
+        [MemberData(nameof(Float16VarcharVectorTestData.GetVarcharVectorInsertTestData), MemberType = typeof(Float16VarcharVectorTestData), DisableDiscoveryEnumeration = true)]
+        public async Task TestVectorDataInsertionAsVarcharAsync(int pattern, string jsonValue, float[] expectedData)
+            => await InsertAndValidateAsVarcharAsync(pattern, jsonValue, expectedData);
+
+        #endregion
+
+        #region Stored Procedure Tests
+
+        [ConditionalFact(typeof(DataTestUtility), nameof(DataTestUtility.AreConnStringsSetup), nameof(DataTestUtility.IsSqlVectorFloat16Supported))]
+        public void TestStoredProcParamsForVectorAsVarchar()
+            => StoredProcRoundTrip(Float16VarcharVectorTestData.TestData);
+
+        [ConditionalFact(typeof(DataTestUtility), nameof(DataTestUtility.AreConnStringsSetup), nameof(DataTestUtility.IsSqlVectorFloat16Supported))]
+        public async Task TestStoredProcParamsForVectorAsVarcharAsync()
+            => await StoredProcRoundTripAsync(Float16VarcharVectorTestData.TestData);
+
+        #endregion
+
+        #region Bulk Copy Tests
+
+        [ConditionalTheory(typeof(DataTestUtility), nameof(DataTestUtility.AreConnStringsSetup), nameof(DataTestUtility.IsSqlVectorFloat16Supported))]
+        [InlineData(1)]
+        [InlineData(2)]
+        public void TestSqlBulkCopyForVectorAsVarchar(int bulkCopySourceMode)
+            => BulkCopyRoundTrip(bulkCopySourceMode, Float16VarcharVectorTestData.TestData);
+
+        [ConditionalTheory(typeof(DataTestUtility), nameof(DataTestUtility.AreConnStringsSetup), nameof(DataTestUtility.IsSqlVectorFloat16Supported))]
+        [InlineData(1)]
+        [InlineData(2)]
+        public async Task TestSqlBulkCopyForVectorAsVarcharAsync(int bulkCopySourceMode)
+            => await BulkCopyRoundTripAsync(bulkCopySourceMode, Float16VarcharVectorTestData.TestData);
+
+        #endregion
+
+        #region Prepared Statement Tests
+
+        [ConditionalFact(typeof(DataTestUtility), nameof(DataTestUtility.AreConnStringsSetup), nameof(DataTestUtility.IsSqlVectorFloat16Supported))]
+        public void TestInsertVectorsAsVarcharWithPrepare()
+            => PreparedInsertRoundTrip();
+
+        #endregion
+    }
+}