Add support for QBit data type

ClickHouse.Driver.Tests/BulkCopy/BulkCopyTests.cs

@@ -681,5 +681,91 @@ public void WriteToServerAsync_WithNullDestinationTableName_ThrowsInvalidOperati
 
         Assert.That(ex.Message, Does.Contain("Destination table not set"));
     }
+
+    [Test]
+    [RequiredFeature(Feature.QBit)]
+    public async Task ShouldInsertQBitFloat32()
+    {
+        var targetTable = "test." + SanitizeTableName("bulk_qbit_float32");
+
+        await connection.ExecuteStatementAsync($"DROP TABLE IF EXISTS {targetTable}");
+        await connection.ExecuteStatementAsync($"CREATE TABLE IF NOT EXISTS {targetTable} (vec QBit(Float32, 9)) ENGINE Memory");
+
+        using var bulkCopy = new ClickHouseBulkCopy(connection)
+        {
+            DestinationTableName = targetTable,
+        };
+
+        var testData = new float[] { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f, 7.0f, 8.0f, 9.0f };
+
+        await bulkCopy.InitAsync();
+        await bulkCopy.WriteToServerAsync([[(object)testData]]);
+
+        Assert.That(bulkCopy.RowsWritten, Is.EqualTo(1));
+
+        using var reader = await connection.ExecuteReaderAsync($"SELECT vec FROM {targetTable}");
+        Assert.That(reader.Read(), Is.True);
+        var result = (float[])reader.GetValue(0);
+        Assert.That(result, Is.EqualTo(testData));
+    }
+
+    [Test]
+    [RequiredFeature(Feature.QBit)]
+    public async Task ShouldInsertQBitFloat64()
+    {
+        var targetTable = "test." + SanitizeTableName("bulk_qbit_float64");
+
+        await connection.ExecuteStatementAsync($"DROP TABLE IF EXISTS {targetTable}");
+        await connection.ExecuteStatementAsync($"CREATE TABLE IF NOT EXISTS {targetTable} (vec QBit(Float64, 8)) ENGINE Memory");
+
+        using var bulkCopy = new ClickHouseBulkCopy(connection)
+        {
+            DestinationTableName = targetTable,
+        };
+
+        var testData = new double[] { 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 };
+
+        await bulkCopy.InitAsync();
+        await bulkCopy.WriteToServerAsync([[(object)testData]]);
+
+        Assert.That(bulkCopy.RowsWritten, Is.EqualTo(1));
+
+        using var reader = await connection.ExecuteReaderAsync($"SELECT vec FROM {targetTable}");
+        Assert.That(reader.Read(), Is.True);
+        var result = (double[])reader.GetValue(0);
+        Assert.That(result, Is.EqualTo(testData));
+    }
+
+    [Test]
+    [RequiredFeature(Feature.QBit)]
+    public async Task ShouldInsertQBitBFloat16()
+    {
+        var targetTable = "test." + SanitizeTableName("bulk_qbit_bfloat16");
+
+        await connection.ExecuteStatementAsync($"DROP TABLE IF EXISTS {targetTable}");
+        await connection.ExecuteStatementAsync($"CREATE TABLE IF NOT EXISTS {targetTable} (vec QBit(BFloat16, 6)) ENGINE Memory");
+
+        using var bulkCopy = new ClickHouseBulkCopy(connection)
+        {
+            DestinationTableName = targetTable,
+        };
+
+        var testData = new float[] { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f };
+
+        await bulkCopy.InitAsync();
+        await bulkCopy.WriteToServerAsync([[(object)testData]]);
+
+        Assert.That(bulkCopy.RowsWritten, Is.EqualTo(1));
+
+        using var reader = await connection.ExecuteReaderAsync($"SELECT vec FROM {targetTable}");
+        Assert.That(reader.Read(), Is.True);
+        var result = (float[])reader.GetValue(0);
+        // BFloat16 has reduced precision, check approximate equality
+        Assert.That(result.Length, Is.EqualTo(testData.Length));
+        for (int i = 0; i < result.Length; i++)
+        {
+            Assert.That(result[i], Is.EqualTo(testData[i]).Within(0.01f));
+        }
+    }
 }
 

ClickHouse.Driver.Tests/SQL/SqlSimpleSelectTests.cs

@@ -244,9 +244,17 @@ public async Task ShouldGetValueDecimal()
     [TestCaseSource(typeof(SqlSimpleSelectTests), nameof(SimpleSelectTypes))]
     public async Task ShouldExecuteRandomDataSelectQuery(string type)
     {
-        if (type.StartsWith("Nested") || type == "Nothing" || type.StartsWith("Variant") || type.StartsWith("Json") || type.Contains("BFloat16") || type.StartsWith("Time"))
+        if (type.StartsWith("Nested") ||
+            type == "Nothing" ||
+            type.StartsWith("Variant") ||
+            type.StartsWith("Json") ||
+            type.Contains("BFloat16") ||
+            type.StartsWith("Time") ||
+            type.StartsWith("QBit"))
+        {
             Assert.Ignore($"Type {type} not supported by generateRandom");
-
+        }
+
         using var reader = await connection.ExecuteReaderAsync($"SELECT * FROM generateRandom('value {type.Replace("'", "\\'")}', 10, 10, 10) LIMIT 100");
         reader.AssertHasFieldCount(1);
     }

ClickHouse.Driver.Tests/Utilities/TestUtilities.cs

@@ -98,6 +98,10 @@ public static ClickHouseConnection GetTestClickHouseConnection(bool compression
         {
             builder["set_enable_time_time64_type"] = 1;
         }
+        if (SupportedFeatures.HasFlag(Feature.QBit))
+        {
+            builder["set_allow_experimental_qbit_type"] = 1;
+        }
 
         var settings = new ClickHouseClientSettings(builder)
         {
@@ -400,6 +404,13 @@ public static IEnumerable<DataTypeSample> GetDataTypeSamples()
             yield return new DataTypeSample("Time64(6)", typeof(TimeSpan), "'-5:25:05.123456'::Time64(6)", (new TimeSpan(5, 25, 5).Add(TimeSpan.FromMilliseconds(123.456)).Negate()));
         }
 
+        if (SupportedFeatures.HasFlag(Feature.QBit))
+        {
+            yield return new DataTypeSample("QBit(Float32, 4)", typeof(float[]), "[1.0, 2.0, 3.0, 4.0]::QBit(Float32, 4)", new float[] { 1f, 2f, 3f, 4f });
+            yield return new DataTypeSample("QBit(Float64, 5)", typeof(double[]), "[1.0, 2.0, 3.0, 4.0, 5.0]::QBit(Float64, 5)", new double[] { 1.0, 2.0, 3.0, 4.0, 5.0 });
+            yield return new DataTypeSample("QBit(BFloat16, 6)", typeof(float[]), "[1.0, 2.0, 3.0, 4.0, 5.0, 6.0]::QBit(BFloat16, 6)", new float[] { 1f, 2f, 3f, 4f, 5f, 6f });
+        }
+
         // Generate composite type tests for ALL base types that FromByteCode supports
         // This ensures that all type decoders work correctly in composite contexts (Array, Nullable, Tuple, Map, Variant)
         var baseTypesToTest = new List<DataTypeSample>

ClickHouse.Driver/ADO/Feature.cs

@@ -48,5 +48,8 @@ public enum Feature
     [SinceVersion("25.6")]
     Time = 1 << 12,
 
+    [SinceVersion("25.10")]
+    QBit = 1 << 13,
+
     All = ~None, // Special value
 }

ClickHouse.Driver/Formats/HttpParameterFormatter.cs

@@ -87,6 +87,9 @@ internal static string Format(ClickHouseType type, object value, bool quote)
             case ArrayType arrayType when value is IEnumerable enumerable:
                 return $"[{string.Join(",", enumerable.Cast<object>().Select(obj => Format(arrayType.UnderlyingType, obj, true)))}]";
 
+            case QBitType qbitType when value is IEnumerable enumerable:
+                return $"[{string.Join(",", enumerable.Cast<object>().Select(obj => Format(qbitType.ElementType, obj, true)))}]";
+
             case NestedType nestedType when value is IEnumerable enumerable:
                 var values = enumerable.Cast<object>().Select(x => Format(nestedType, x, false));
                 return $"[{string.Join(",", values)}]";

ClickHouse.Driver/Types/BinaryTypeDecoder.cs

@@ -157,6 +157,9 @@ internal static ClickHouseType FromByteCode(ExtendedBinaryReader reader, TypeSet
                     Scale = reader.Read7BitEncodedInt(),
                 };
 
+            case BinaryTypeIndex.QBit:
+                return DecodeQBit(reader, typeSettings);
+
             default:
                 break;
         }
@@ -302,6 +305,13 @@ private static ClickHouseType DecodeCustomType(ExtendedBinaryReader reader)
         }
     }
 
+    private static QBitType DecodeQBit(ExtendedBinaryReader reader, TypeSettings typeSettings)
+    {
+        var elementType = FromByteCode(reader, typeSettings);
+        var dimension = reader.Read7BitEncodedInt();
+        return new QBitType { ElementType = elementType, Dimension = dimension };
+    }
+
     private static JsonType DecodeJson(ExtendedBinaryReader reader, TypeSettings typeSettings)
     {
         var serializationVersion = reader.ReadByte();

ClickHouse.Driver/Types/QBitType.cs

@@ -0,0 +1,58 @@
+using System;
+using System.Globalization;
+using ClickHouse.Driver.Formats;
+using ClickHouse.Driver.Types.Grammar;
+
+namespace ClickHouse.Driver.Types;
+
+/// <summary>
+/// Represents the ClickHouse QBit type: a quantized vector type for efficient storage.
+/// On the wire, QBit is simply an Array of the underlying element type (Float32/Float64/BFloat16).
+/// The bit-transpose optimization happens server-side for storage, not in the wire protocol.
+/// </summary>
+internal class QBitType : ParameterizedType
+{
+    // Delegate to ArrayType for wire format
+    private ArrayType UnderlyingArrayType => new ArrayType { UnderlyingType = ElementType };
+
+    public ClickHouseType ElementType { get; set; }
+    public int Dimension { get; set; }
+
+    public override Type FrameworkType => ElementType.FrameworkType.MakeArrayType();
+
+    public override string Name => "QBit";
+
+    public override ParameterizedType Parse(SyntaxTreeNode node, Func<SyntaxTreeNode, ClickHouseType> parseClickHouseTypeFunc, TypeSettings settings)
+    {
+        return new QBitType
+        {
+            ElementType = parseClickHouseTypeFunc(node.ChildNodes[0]),
+            Dimension = int.Parse(node.ChildNodes[1].Value, CultureInfo.InvariantCulture),
+        };
+    }
+
+    public override string ToString() => $"{Name}({ElementType},{Dimension})";
+
+    public override object Read(ExtendedBinaryReader reader)
+    {
+        // QBit wire format is Array(UnderlyingType), but the length is padded to the nearest 8
+        var length = reader.Read7BitEncodedInt();
+        var data = Array.CreateInstance(ElementType.FrameworkType, Dimension); // Could use a pool here
+        for (var i = 0; i < length; i++)
+        {
+            var value = ElementType.Read(reader);
+            if (i < Dimension)
+            {
+                data.SetValue(ClearDBNull(value), i);
+            }
+        }
+
+        return data;
+    }
+
+    public override void Write(ExtendedBinaryWriter writer, object value)
+    {
+        // QBit wire format is just Array(ElementType)
+        UnderlyingArrayType.Write(writer, value);
+    }
+}

ClickHouse.Driver/Types/TypeConverter.cs

@@ -177,6 +177,8 @@ static TypeConverter()
 
         RegisterParameterizedType<AggregateFunctionType>();
 
+        RegisterParameterizedType<QBitType>();
+
         // Mapping fixups
         ReverseMapping.Add(typeof(ClickHouseDecimal), new Decimal128Type());
         ReverseMapping.Add(typeof(decimal), new Decimal128Type());

examples/Vector_001_QBitSimilaritySearch.cs

@@ -0,0 +1,111 @@
+using ClickHouse.Driver.ADO;
+using ClickHouse.Driver.Utility;
+
+namespace ClickHouse.Driver.Examples;
+
+/// <summary>
+/// Demonstrates using QBit vectors for similarity search in ClickHouse.
+/// QBit is a quantized vector type that provides efficient storage with configurable precision.
+/// This example shows semantic similarity search with different precision levels using L2DistanceTransposed.
+/// </summary>
+public static class QBitSimilaritySearch
+{
+    public static async Task Run()
+    {
+        using var connection = new ClickHouseConnection("Host=localhost");
+        await connection.OpenAsync();
+
+        Console.WriteLine("=== QBit Similarity Search with Different Precision Levels ===\n");
+
+        var tableName = "example_qbit_similarity";
+
+        await connection.ExecuteStatementAsync($"DROP TABLE IF EXISTS {tableName}");
+        await connection.ExecuteStatementAsync($@"
+            CREATE TABLE {tableName}
+            (
+                word String,
+                vec QBit(Float32, 5)
+            )
+            ENGINE = MergeTree
+            ORDER BY word
+        ");
+
+        // Insert sample word embeddings (simplified 5-dimensional vectors)
+        // In practice, these would come from an embedding model
+        await connection.ExecuteStatementAsync($@"
+            INSERT INTO {tableName} VALUES
+            ('apple',  [0.9, 0.1, 0.8, 0.2, 0.7]),
+            ('banana', [0.85, 0.15, 0.75, 0.25, 0.65]),
+            ('orange', [0.88, 0.12, 0.78, 0.22, 0.68]),
+            ('dog',    [0.1, 0.9, 0.2, 0.8, 0.3]),
+            ('horse',  [0.15, 0.85, 0.25, 0.75, 0.35]),
+            ('cat',    [0.12, 0.88, 0.22, 0.78, 0.32])
+        ");
+
+        Console.WriteLine("Inserted 6 words with 5-dimensional QBit(Float32, 5) embeddings\n");
+
+        // Query vector: looking for words similar to "apple"
+        var queryVector = "[0.9, 0.1, 0.8, 0.2, 0.7]";
+
+        // Example 1: High precision search (32 bits per component)
+        Console.WriteLine("=== High Precision Search (32 bits) ===");
+        Console.WriteLine("Using L2DistanceTransposed with precision=32\n");
+
+        using (var reader = await connection.ExecuteReaderAsync($@"
+            SELECT
+                word,
+                L2DistanceTransposed(vec, {queryVector}, 32) AS distance
+            FROM {tableName}
+            ORDER BY distance
+        "))
+        {
+            Console.WriteLine("Word\t\tDistance");
+            Console.WriteLine("----\t\t--------");
+
+            while (reader.Read())
+            {
+                var word = reader.GetString(0);
+                var distance = reader.GetFloat(1);
+                Console.WriteLine($"{word,-12}\t{distance:F6}");
+            }
+        }
+
+        // Example 2: Low precision search (12 bits per component) - faster but less accurate
+        Console.WriteLine("\n=== Low Precision Search (12 bits) ===");
+        Console.WriteLine("Using L2DistanceTransposed with precision=12\n");
+
+        using (var reader = await connection.ExecuteReaderAsync($@"
+            SELECT
+                word,
+                L2DistanceTransposed(vec, {queryVector}, 12) AS distance
+            FROM {tableName}
+            ORDER BY distance
+        "))
+        {
+            Console.WriteLine("Word\t\tDistance");
+            Console.WriteLine("----\t\t--------");
+
+            while (reader.Read())
+            {
+                var word = reader.GetString(0);
+                var distance = reader.GetFloat(1);
+                Console.WriteLine($"{word,-12}\t{distance:F6}");
+            }
+        }
+
+        // Read vector data back as float[]
+        Console.WriteLine("\n=== Reading QBit Data ===\n");
+        using (var reader = await connection.ExecuteReaderAsync($"SELECT word, vec FROM {tableName} LIMIT 3"))
+        {
+            while (reader.Read())
+            {
+                var word = reader.GetString(0);
+                var vec = (float[])reader.GetValue(1);
+                Console.WriteLine($"{word}: [{string.Join(", ", vec.Select(v => v.ToString("F2")))}]");
+            }
+        }
+
+        await connection.ExecuteStatementAsync($"DROP TABLE IF EXISTS {tableName}");
+        Console.WriteLine($"\nCleaned up table '{tableName}'");
+    }
+}