feat(csharp): add shared schema factories and GetInfo builder

Add MetadataSchemaFactory to MetadataSchemaDefinitions.cs with:
- Schema factories: CreateCatalogsSchema, CreateSchemasSchema,
  CreateTablesSchema, CreateColumnMetadataSchema, CreatePrimaryKeysSchema,
  CreateCrossReferenceSchema
- Empty result helpers: CreateEmpty*Result for each schema type
- Result builders: BuildPrimaryKeysResult, BuildCrossReferenceResult
- BuildGetInfoResult: shared DenseUnionArray builder for GetInfo

Refactor HiveServer2Connection.GetInfo to use BuildGetInfoResult,
replacing ~150 lines of inline DenseUnionArray construction.
Values are now lazily resolved per requested info code.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: msrathore-db

csharp/src/Hive2/HiveServer2Connection.cs

@@ -1317,152 +1317,29 @@ public override IArrowArrayStream GetInfo(IReadOnlyList<AdbcInfoCode> codes)
         {
             return this.TraceActivity(activity =>
             {
-                const int strValTypeID = 0;
-                const int boolValTypeId = 1;
-
-                UnionType infoUnionType = new UnionType(
-                    new Field[]
-                    {
-                    new Field("string_value", StringType.Default, true),
-                    new Field("bool_value", BooleanType.Default, true),
-                    new Field("int64_value", Int64Type.Default, true),
-                    new Field("int32_bitmask", Int32Type.Default, true),
-                    new Field(
-                        "string_list",
-                        new ListType(
-                            new Field("item", StringType.Default, true)
-                        ),
-                        false
-                    ),
-                    new Field(
-                        "int32_to_int32_list_map",
-                        new ListType(
-                            new Field("entries", new StructType(
-                                new Field[]
-                                {
-                                    new Field("key", Int32Type.Default, false),
-                                    new Field("value", Int32Type.Default, true),
-                                }
-                                ), false)
-                        ),
-                        true
-                    )
-                    },
-                    new int[] { 0, 1, 2, 3, 4, 5 },
-                    UnionMode.Dense);
-
                 if (codes.Count == 0)
-                {
                     codes = infoSupportedCodes;
-                }
-
-                UInt32Array.Builder infoNameBuilder = new UInt32Array.Builder();
-                ArrowBuffer.Builder<byte> typeBuilder = new ArrowBuffer.Builder<byte>();
-                ArrowBuffer.Builder<int> offsetBuilder = new ArrowBuffer.Builder<int>();
-                StringArray.Builder stringInfoBuilder = new StringArray.Builder();
-                BooleanArray.Builder booleanInfoBuilder = new BooleanArray.Builder();
 
-                int nullCount = 0;
-                int arrayLength = codes.Count;
-                int offset = 0;
-
-                foreach (AdbcInfoCode code in codes)
+                var values = new Dictionary<AdbcInfoCode, object>();
+                foreach (var code in codes)
                 {
-                    string tagKey = SemanticConventions.Db.Operation.Parameter(code.ToString().ToLowerInvariant());
-                    Func<object?> tagValue = () => null;
-                    switch (code)
+                    object? val = code switch
                     {
-                        case AdbcInfoCode.DriverName:
-                            infoNameBuilder.Append((uint)code);
-                            typeBuilder.Append(strValTypeID);
-                            offsetBuilder.Append(offset++);
-                            stringInfoBuilder.Append(InfoDriverName);
-                            booleanInfoBuilder.AppendNull();
-                            tagValue = () => InfoDriverName;
-                            break;
-                        case AdbcInfoCode.DriverVersion:
-                            infoNameBuilder.Append((uint)code);
-                            typeBuilder.Append(strValTypeID);
-                            offsetBuilder.Append(offset++);
-                            stringInfoBuilder.Append(ProductVersion);
-                            booleanInfoBuilder.AppendNull();
-                            tagValue = () => ProductVersion;
-                            break;
-                        case AdbcInfoCode.DriverArrowVersion:
-                            infoNameBuilder.Append((uint)code);
-                            typeBuilder.Append(strValTypeID);
-                            offsetBuilder.Append(offset++);
-                            stringInfoBuilder.Append(InfoDriverArrowVersion);
-                            booleanInfoBuilder.AppendNull();
-                            tagValue = () => InfoDriverArrowVersion;
-                            break;
-                        case AdbcInfoCode.VendorName:
-                            infoNameBuilder.Append((uint)code);
-                            typeBuilder.Append(strValTypeID);
-                            offsetBuilder.Append(offset++);
-                            string vendorName = VendorName;
-                            stringInfoBuilder.Append(vendorName);
-                            booleanInfoBuilder.AppendNull();
-                            tagValue = () => vendorName;
-                            break;
-                        case AdbcInfoCode.VendorVersion:
-                            infoNameBuilder.Append((uint)code);
-                            typeBuilder.Append(strValTypeID);
-                            offsetBuilder.Append(offset++);
-                            string? vendorVersion = VendorVersion;
-                            stringInfoBuilder.Append(vendorVersion);
-                            booleanInfoBuilder.AppendNull();
-                            tagValue = () => vendorVersion;
-                            break;
-                        case AdbcInfoCode.VendorSql:
-                            infoNameBuilder.Append((uint)code);
-                            typeBuilder.Append(boolValTypeId);
-                            offsetBuilder.Append(offset++);
-                            stringInfoBuilder.AppendNull();
-                            booleanInfoBuilder.Append(InfoVendorSql);
-                            tagValue = () => InfoVendorSql;
-                            break;
-                        default:
-                            infoNameBuilder.Append((uint)code);
-                            typeBuilder.Append(strValTypeID);
-                            offsetBuilder.Append(offset++);
-                            stringInfoBuilder.AppendNull();
-                            booleanInfoBuilder.AppendNull();
-                            nullCount++;
-                            break;
-                    }
-                    ActivityExtensions.AddTag(activity, tagKey, tagValue);
-                }
-
-                StructType entryType = new StructType(
-                    new Field[] {
-                    new Field("key", Int32Type.Default, false),
-                    new Field("value", Int32Type.Default, true)});
-
-                StructArray entriesDataArray = new StructArray(entryType, 0,
-                    new[] { new Int32Array.Builder().Build(), new Int32Array.Builder().Build() },
-                    new ArrowBuffer.BitmapBuilder().Build());
-
-                IArrowArray[] childrenArrays = new IArrowArray[]
-                {
-                stringInfoBuilder.Build(),
-                booleanInfoBuilder.Build(),
-                new Int64Array.Builder().Build(),
-                new Int32Array.Builder().Build(),
-                new ListArray.Builder(StringType.Default).Build(),
-                new List<IArrowArray?>(){ entriesDataArray }.BuildListArrayForType(entryType)
-                };
-
-                DenseUnionArray infoValue = new DenseUnionArray(infoUnionType, arrayLength, childrenArrays, typeBuilder.Build(), offsetBuilder.Build(), nullCount);
+                        AdbcInfoCode.DriverName => InfoDriverName,
+                        AdbcInfoCode.DriverVersion => ProductVersion,
+                        AdbcInfoCode.DriverArrowVersion => InfoDriverArrowVersion,
+                        AdbcInfoCode.VendorName => VendorName,
+                        AdbcInfoCode.VendorVersion => VendorVersion ?? "",
+                        AdbcInfoCode.VendorSql => InfoVendorSql,
+                        _ => null
+                    };
+                    if (val != null) values[code] = val;
 
-                IArrowArray[] dataArrays = new IArrowArray[]
-                {
-                infoNameBuilder.Build(),
-                infoValue
-                };
-                StandardSchemas.GetInfoSchema.Validate(dataArrays);
+                    string tagKey = SemanticConventions.Db.Operation.Parameter(code.ToString().ToLowerInvariant());
+                    ActivityExtensions.AddTag(activity, tagKey, () => val);
+                }
 
-                return new HiveInfoArrowStream(StandardSchemas.GetInfoSchema, dataArrays);
+                return MetadataSchemaFactory.BuildGetInfoResult(codes, values);
             }, ClassName + "." + nameof(GetInfo));
         }