feat(csharp): support native SEA metadata results

csharp/src/FlatColumnsResultBuilder.cs

@@ -15,7 +15,11 @@
  */
 
 using System.Collections.Generic;
-using AdbcDrivers.Databricks.StatementExecution;using AdbcDrivers.HiveServer2;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using AdbcDrivers.Databricks.StatementExecution;
+using AdbcDrivers.HiveServer2;
 using AdbcDrivers.HiveServer2.Hive2;
 using Apache.Arrow;
 using Apache.Arrow.Adbc;
@@ -29,6 +33,58 @@ namespace AdbcDrivers.Databricks
     /// </summary>
     internal static class FlatColumnsResultBuilder
     {
+        internal static async Task<QueryResult> BuildFlatColumnsResultAsync(
+            ColumnMetadataResult columns, CancellationToken cancellationToken)
+        {
+            var schema = MetadataSchemaFactory.CreateColumnMetadataSchema();
+            if (columns.IsNative)
+                return NativeMetadataResultBuilder.Build(columns.Results, schema, MetadataOperation.GetColumns);
+            if (!columns.Results.Any(result => result.IsNative && result.Batches.Count > 0))
+                return BuildFlatColumnsResult(columns.Rows);
+
+            // Normalize each response independently so SHOW fallback cannot discard native fields.
+            var batches = new List<RecordBatch>();
+            try
+            {
+                for (int index = 0; index < columns.Results.Count; index++)
+                {
+                    var result = columns.Results[index];
+                    var flat = result.IsNative
+                        ? NativeMetadataResultBuilder.Build(result, schema, MetadataOperation.GetColumns)
+                        : BuildFlatColumnsResult(columns.RowsByResult[index]);
+                    using var stream = flat.Stream!;
+                    var batch = await stream.ReadNextRecordBatchAsync(cancellationToken).ConfigureAwait(false);
+                    if (batch != null) batches.Add(batch);
+                }
+
+                var arrays = Enumerable.Range(0, schema.FieldsList.Count)
+                    .Select(column => ArrowArrayFactory.BuildArray(ArrayDataConcatenator.Concatenate(
+                        batches.Select(batch => batch.Column(column).Data).ToList())!))
+                    .ToArray();
+                return new QueryResult(batches.Sum(batch => batch.Length), new HiveInfoArrowStream(schema, arrays));
+            }
+            finally
+            {
+                foreach (var batch in batches) batch.Dispose();
+            }
+        }
+
+        private static QueryResult BuildFlatColumnsResult(IEnumerable<ColumnRow> columns)
+        {
+            var tableInfos = new Dictionary<string, (string catalog, string schema, string table, TableInfo info)>();
+            foreach (var column in columns)
+            {
+                if (column.Catalog == null || column.Schema == null || column.Table == null) continue;
+                string key = $"{column.Catalog}.{column.Schema}.{column.Table}";
+                if (!tableInfos.ContainsKey(key))
+                    tableInfos[key] = (column.Catalog, column.Schema, column.Table, new TableInfo("TABLE"));
+                ColumnMetadataHelper.PopulateTableInfoFromTypeName(
+                    tableInfos[key].info, column.Name, column.TypeName, column.Ordinal, column.Nullable,
+                    columnDefault: column.Default, isAutoIncrement: column.IsAutoIncrement);
+            }
+            return BuildFlatColumnsResult(tableInfos.Values);
+        }
+
         internal static QueryResult BuildFlatColumnsResult(
             IEnumerable<(string catalog, string schema, string table, TableInfo info)> tables)
         {
@@ -81,7 +137,8 @@ internal static QueryResult BuildFlatColumnsResult(
 
                     nullableBuilder.Append(info.Nullable[i]);
                     remarksBuilder.Append("");
-                    columnDefBuilder.AppendNull();
+                    if (string.IsNullOrEmpty(info.ColumnDefault[i])) columnDefBuilder.AppendNull();
+                    else columnDefBuilder.Append(info.ColumnDefault[i]);
 
                     sqlDataTypeBuilder.Append(info.ColType[i]);
 

csharp/src/StatementExecution/ColumnMetadataHelper.cs

@@ -184,6 +184,24 @@ internal static string GetBaseTypeName(string typeName)
             };
         }
 
+        internal static (long ColumnSize, long DecimalDigits) NormalizePrecisionAndScale(
+            string? typeName, long? columnSize, long? decimalDigits)
+        {
+            if (typeName != null)
+            {
+                string baseName = GetBaseTypeName(typeName);
+                if (baseName is "DECIMAL" or "NUMERIC")
+                {
+                    columnSize = GetColumnSizeDefault(typeName);
+                    decimalDigits = GetDecimalDigitsDefault(typeName);
+                }
+                else if (s_charBaseTypes.Contains(baseName))
+                    columnSize = GetColumnSizeDefault(typeName);
+            }
+            // Thrift defaults null sizes and digits to zero before type-specific overrides.
+            return (columnSize ?? 0, decimalDigits ?? 0);
+        }
+
         internal static int? GetBufferLength(string typeName)
         {
             string baseName = GetBaseTypeName(typeName);
@@ -242,19 +260,21 @@ internal static void PopulateTableInfoFromTypeName(
             int ordinalPosition,
             bool isNullable = true,
             string? comment = null,
-            string? columnDefault = null)
+            string? columnDefault = null,
+            bool isAutoIncrement = false)
         {
             tableInfo.ColumnName.Add(columnName);
             tableInfo.TypeName.Add(typeName);
             tableInfo.ColType.Add(GetDataTypeCode(typeName));
             tableInfo.BaseTypeName.Add(GetBaseTypeName(typeName));
-            tableInfo.Precision.Add(GetColumnSizeDefault(typeName));
-            int? scale = GetDecimalDigitsDefault(typeName);
-            tableInfo.Scale.Add(scale.HasValue ? (short)scale.Value : null);
+            var precisionAndScale = NormalizePrecisionAndScale(
+                typeName, GetColumnSizeDefault(typeName), GetDecimalDigitsDefault(typeName));
+            tableInfo.Precision.Add(checked((int)precisionAndScale.ColumnSize));
+            tableInfo.Scale.Add((short)precisionAndScale.DecimalDigits);
             tableInfo.OrdinalPosition.Add(ordinalPosition);
             tableInfo.Nullable.Add(isNullable ? (short)1 : (short)0);
             tableInfo.IsNullable.Add(isNullable ? "YES" : "NO");
-            tableInfo.IsAutoIncrement.Add(false);
+            tableInfo.IsAutoIncrement.Add(isAutoIncrement);
             tableInfo.ColumnDefault.Add(columnDefault ?? "");
         }