feat(csharp): complete Statement Execution API metadata implementation

csharp/src/ColumnMetadataSchemas.cs

@@ -0,0 +1,310 @@
+/*
+* Copyright (c) 2025 ADBC Drivers Contributors
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*     http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+using Apache.Arrow;
+using Apache.Arrow.Types;
+
+namespace AdbcDrivers.Databricks
+{
+    /// <summary>
+    /// Shared helper class for standard metadata schemas.
+    /// Used by both Thrift and Statement Execution API protocols to ensure consistent metadata structure.
+    /// Provides schemas for GetCatalogs, GetSchemas, GetTables, GetColumns, GetPrimaryKeys, GetCrossReference.
+    /// </summary>
+    internal static class ColumnMetadataSchemas
+    {
+        #region GetColumns Schema (24 columns)
+
+        /// <summary>
+        /// Creates the standard GetColumns schema.
+        /// This schema follows the standard flat table format for column metadata.
+        /// </summary>
+        /// <returns>Schema with 24 column definitions</returns>
+        public static Schema CreateColumnMetadataSchema()
+        {
+            var fields = new[]
+            {
+                new Field("TABLE_CAT", StringType.Default, true),
+                new Field("TABLE_SCHEM", StringType.Default, true),
+                new Field("TABLE_NAME", StringType.Default, true),
+                new Field("COLUMN_NAME", StringType.Default, true),
+                new Field("DATA_TYPE", Int32Type.Default, true),
+                new Field("TYPE_NAME", StringType.Default, true),
+                new Field("COLUMN_SIZE", Int32Type.Default, true),
+                new Field("BUFFER_LENGTH", Int8Type.Default, true),
+                new Field("DECIMAL_DIGITS", Int32Type.Default, true),
+                new Field("NUM_PREC_RADIX", Int32Type.Default, true),
+                new Field("NULLABLE", Int32Type.Default, true),
+                new Field("REMARKS", StringType.Default, true),
+                new Field("COLUMN_DEF", StringType.Default, true),
+                new Field("SQL_DATA_TYPE", Int32Type.Default, true),
+                new Field("SQL_DATETIME_SUB", Int32Type.Default, true),
+                new Field("CHAR_OCTET_LENGTH", Int32Type.Default, true),
+                new Field("ORDINAL_POSITION", Int32Type.Default, true),
+                new Field("IS_NULLABLE", StringType.Default, true),
+                new Field("SCOPE_CATALOG", StringType.Default, true),
+                new Field("SCOPE_SCHEMA", StringType.Default, true),
+                new Field("SCOPE_TABLE", StringType.Default, true),
+                new Field("SOURCE_DATA_TYPE", Int16Type.Default, true),
+                new Field("IS_AUTO_INCREMENT", StringType.Default, true),
+                new Field("BASE_TYPE_NAME", StringType.Default, true)
+            };
+            return new Schema(fields, null);
+        }
+
+        /// <summary>
+        /// Creates empty Arrow arrays for each column in the column metadata schema.
+        /// Useful for returning empty results from metadata queries.
+        /// </summary>
+        /// <returns>Array of empty Arrow arrays</returns>
+        public static IArrowArray[] CreateColumnMetadataEmptyArray()
+        {
+            return
+            [
+                new StringArray.Builder().Build(), // TABLE_CAT
+                new StringArray.Builder().Build(), // TABLE_SCHEM
+                new StringArray.Builder().Build(), // TABLE_NAME
+                new StringArray.Builder().Build(), // COLUMN_NAME
+                new Int32Array.Builder().Build(),  // DATA_TYPE
+                new StringArray.Builder().Build(), // TYPE_NAME
+                new Int32Array.Builder().Build(),  // COLUMN_SIZE
+                new Int8Array.Builder().Build(),   // BUFFER_LENGTH
+                new Int32Array.Builder().Build(),  // DECIMAL_DIGITS
+                new Int32Array.Builder().Build(),  // NUM_PREC_RADIX
+                new Int32Array.Builder().Build(),  // NULLABLE
+                new StringArray.Builder().Build(), // REMARKS
+                new StringArray.Builder().Build(), // COLUMN_DEF
+                new Int32Array.Builder().Build(),  // SQL_DATA_TYPE
+                new Int32Array.Builder().Build(),  // SQL_DATETIME_SUB
+                new Int32Array.Builder().Build(),  // CHAR_OCTET_LENGTH
+                new Int32Array.Builder().Build(),  // ORDINAL_POSITION
+                new StringArray.Builder().Build(), // IS_NULLABLE
+                new StringArray.Builder().Build(), // SCOPE_CATALOG
+                new StringArray.Builder().Build(), // SCOPE_SCHEMA
+                new StringArray.Builder().Build(), // SCOPE_TABLE
+                new Int16Array.Builder().Build(),  // SOURCE_DATA_TYPE
+                new StringArray.Builder().Build(), // IS_AUTO_INCREMENT
+                new StringArray.Builder().Build()  // BASE_TYPE_NAME
+            ];
+        }
+
+        #endregion
+
+        #region GetCatalogs Schema (1 column)
+
+        /// <summary>
+        /// Creates the standard GetCatalogs schema (1 column: TABLE_CAT).
+        /// Follows JDBC DatabaseMetaData.getCatalogs() convention.
+        /// </summary>
+        /// <returns>Schema with TABLE_CAT column</returns>
+        public static Schema CreateCatalogsSchema()
+        {
+            var fields = new[]
+            {
+                new Field("TABLE_CAT", StringType.Default, true)
+            };
+            return new Schema(fields, null);
+        }
+
+        /// <summary>
+        /// Creates empty Arrow arrays for GetCatalogs schema.
+        /// </summary>
+        /// <returns>Array of empty Arrow arrays (1 column)</returns>
+        public static IArrowArray[] CreateCatalogsEmptyArray()
+        {
+            return
+            [
+                new StringArray.Builder().Build() // TABLE_CAT
+            ];
+        }
+
+        #endregion
+
+        #region GetSchemas Schema (2 columns)
+
+        /// <summary>
+        /// Creates the standard GetSchemas schema (2 columns: TABLE_SCHEM, TABLE_CATALOG).
+        /// Follows JDBC DatabaseMetaData.getSchemas() convention.
+        /// </summary>
+        /// <returns>Schema with TABLE_SCHEM and TABLE_CATALOG columns</returns>
+        public static Schema CreateSchemasSchema()
+        {
+            var fields = new[]
+            {
+                new Field("TABLE_SCHEM", StringType.Default, true),
+                new Field("TABLE_CATALOG", StringType.Default, true)
+            };
+            return new Schema(fields, null);
+        }
+
+        /// <summary>
+        /// Creates empty Arrow arrays for GetSchemas schema.
+        /// </summary>
+        /// <returns>Array of empty Arrow arrays (2 columns)</returns>
+        public static IArrowArray[] CreateSchemasEmptyArray()
+        {
+            return
+            [
+                new StringArray.Builder().Build(), // TABLE_SCHEM
+                new StringArray.Builder().Build()  // TABLE_CATALOG
+            ];
+        }
+
+        #endregion
+
+        #region GetTables Schema (10 columns)
+
+        /// <summary>
+        /// Creates the standard GetTables schema (10 columns).
+        /// Follows JDBC DatabaseMetaData.getTables() convention.
+        /// </summary>
+        /// <returns>Schema with 10 table metadata columns</returns>
+        public static Schema CreateTablesSchema()
+        {
+            var fields = new[]
+            {
+                new Field("TABLE_CAT", StringType.Default, true),
+                new Field("TABLE_SCHEM", StringType.Default, true),
+                new Field("TABLE_NAME", StringType.Default, true),
+                new Field("TABLE_TYPE", StringType.Default, true),
+                new Field("REMARKS", StringType.Default, true),
+                new Field("TYPE_CAT", StringType.Default, true),
+                new Field("TYPE_SCHEM", StringType.Default, true),
+                new Field("TYPE_NAME", StringType.Default, true),
+                new Field("SELF_REFERENCING_COL_NAME", StringType.Default, true),
+                new Field("REF_GENERATION", StringType.Default, true)
+            };
+            return new Schema(fields, null);
+        }
+
+        /// <summary>
+        /// Creates empty Arrow arrays for GetTables schema.
+        /// </summary>
+        /// <returns>Array of empty Arrow arrays (10 columns)</returns>
+        public static IArrowArray[] CreateTablesEmptyArray()
+        {
+            return
+            [
+                new StringArray.Builder().Build(), // TABLE_CAT
+                new StringArray.Builder().Build(), // TABLE_SCHEM
+                new StringArray.Builder().Build(), // TABLE_NAME
+                new StringArray.Builder().Build(), // TABLE_TYPE
+                new StringArray.Builder().Build(), // REMARKS
+                new StringArray.Builder().Build(), // TYPE_CAT
+                new StringArray.Builder().Build(), // TYPE_SCHEM
+                new StringArray.Builder().Build(), // TYPE_NAME
+                new StringArray.Builder().Build(), // SELF_REFERENCING_COL_NAME
+                new StringArray.Builder().Build()  // REF_GENERATION
+            ];
+        }
+
+        #endregion
+
+        #region GetPrimaryKeys Schema (6 columns)
+
+        /// <summary>
+        /// Creates the standard GetPrimaryKeys schema (6 columns).
+        /// </summary>
+        /// <returns>Schema with 6 primary key metadata columns</returns>
+        public static Schema CreatePrimaryKeySchema()
+        {
+            var fields = new[]
+            {
+                new Field("TABLE_CAT", StringType.Default, true),
+                new Field("TABLE_SCHEM", StringType.Default, true),
+                new Field("TABLE_NAME", StringType.Default, true),
+                new Field("COLUMN_NAME", StringType.Default, true),
+                new Field("KEQ_SEQ", Int32Type.Default, true),
+                new Field("PK_NAME", StringType.Default, true)
+            };
+            return new Schema(fields, null);
+        }
+
+        /// <summary>
+        /// Creates empty Arrow arrays for GetPrimaryKeys schema.
+        /// </summary>
+        /// <returns>Array of empty Arrow arrays (6 columns)</returns>
+        public static IArrowArray[] CreatePrimaryKeyEmptyArray()
+        {
+            return
+            [
+                new StringArray.Builder().Build(), // TABLE_CAT
+                new StringArray.Builder().Build(), // TABLE_SCHEM
+                new StringArray.Builder().Build(), // TABLE_NAME
+                new StringArray.Builder().Build(), // COLUMN_NAME
+                new Int32Array.Builder().Build(),  // KEQ_SEQ
+                new StringArray.Builder().Build()  // PK_NAME
+            ];
+        }
+
+        #endregion
+
+        #region GetCrossReference (Foreign Keys) Schema (14 columns)
+
+        /// <summary>
+        /// Creates the standard GetCrossReference schema (14 columns).
+        /// </summary>
+        /// <returns>Schema with 14 foreign key metadata columns</returns>
+        public static Schema CreateForeignKeySchema()
+        {
+            var fields = new[]
+            {
+                new Field("PKTABLE_CAT", StringType.Default, true),
+                new Field("PKTABLE_SCHEM", StringType.Default, true),
+                new Field("PKTABLE_NAME", StringType.Default, true),
+                new Field("PKCOLUMN_NAME", StringType.Default, true),
+                new Field("FKTABLE_CAT", StringType.Default, true),
+                new Field("FKTABLE_SCHEM", StringType.Default, true),
+                new Field("FKTABLE_NAME", StringType.Default, true),
+                new Field("FKCOLUMN_NAME", StringType.Default, true),
+                new Field("KEQ_SEQ", Int32Type.Default, true),
+                new Field("UPDATE_RULE", Int32Type.Default, true),
+                new Field("DELETE_RULE", Int32Type.Default, true),
+                new Field("FK_NAME", StringType.Default, true),
+                new Field("PK_NAME", StringType.Default, true),
+                new Field("DEFERRABILITY", Int32Type.Default, true)
+            };
+            return new Schema(fields, null);
+        }
+
+        /// <summary>
+        /// Creates empty Arrow arrays for GetCrossReference schema.
+        /// </summary>
+        /// <returns>Array of empty Arrow arrays (14 columns)</returns>
+        public static IArrowArray[] CreateForeignKeyEmptyArray()
+        {
+            return
+            [
+                new StringArray.Builder().Build(), // PKTABLE_CAT
+                new StringArray.Builder().Build(), // PKTABLE_SCHEM
+                new StringArray.Builder().Build(), // PKTABLE_NAME
+                new StringArray.Builder().Build(), // PKCOLUMN_NAME
+                new StringArray.Builder().Build(), // FKTABLE_CAT
+                new StringArray.Builder().Build(), // FKTABLE_SCHEM
+                new StringArray.Builder().Build(), // FKTABLE_NAME
+                new StringArray.Builder().Build(), // FKCOLUMN_NAME
+                new Int32Array.Builder().Build(),  // KEQ_SEQ
+                new Int32Array.Builder().Build(),  // UPDATE_RULE
+                new Int32Array.Builder().Build(),  // DELETE_RULE
+                new StringArray.Builder().Build(), // FK_NAME
+                new StringArray.Builder().Build(), // PK_NAME
+                new Int32Array.Builder().Build()   // DEFERRABILITY
+            ];
+        }
+
+        #endregion
+    }
+}