feat(csharp): implement SEA metadata — GetObjects, GetTableSchema, GetTableTypes

Core SEA metadata implementation with connection-level and statement-level support:

Connection-level:
- Implement IGetObjectsDataProvider for SEA (GetCatalogs, GetSchemas,
  GetTables, PopulateColumnInfo via SHOW SQL commands)
- Implement GetObjects using shared GetObjectsResultBuilder
- Implement GetTableSchema via SHOW COLUMNS + shared GetArrowType
- Implement GetTableTypes returning TABLE and VIEW
- Implement GetInfo via shared MetadataSchemaFactory.BuildGetInfoResult
- Add CancellationToken support with configurable timeout
- Add activity tracing on all metadata methods

Statement-level:
- Add metadata command routing (GetCatalogs/Schemas/Tables/Columns/
  ColumnsExtended/PrimaryKeys/CrossReference/TableTypes)
- Reuse DatabricksStatement.CreateExtendedColumnsResult for GetColumnsExtended
- Wire NormalizeSparkCatalog for SPARK catalog compatibility

New files:
- MetadataCommandBase + Show*Command classes (SQL builders)
- MetadataUtilities (catalog normalization, PK/FK validation)
- Refactor DescTableExtendedResult to use shared ColumnMetadataHelper
- Wire DatabricksStatement to shared MetadataSchemaFactory

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

Author: msrathore-db

csharp/src/DatabricksStatement.cs

@@ -0,0 +1,70 @@
+/*
+ * 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 System;
+
+namespace AdbcDrivers.Databricks
+{
+    internal static class MetadataUtilities
+    {
+        internal static string? NormalizeSparkCatalog(string? catalogName)
+        {
+            if (string.IsNullOrEmpty(catalogName))
+                return catalogName;
+
+            if (string.Equals(catalogName, "SPARK", StringComparison.OrdinalIgnoreCase))
+                return null;
+
+            return catalogName;
+        }
+
+        internal static bool IsInvalidPKFKCatalog(string? catalogName)
+        {
+            return string.IsNullOrEmpty(catalogName) ||
+                   string.Equals(catalogName, "SPARK", StringComparison.OrdinalIgnoreCase) ||
+                   string.Equals(catalogName, "hive_metastore", StringComparison.OrdinalIgnoreCase);
+        }
+
+        internal static bool ShouldReturnEmptyPKFKResult(string? catalogName, string? foreignCatalogName, bool enablePKFK)
+        {
+            if (!enablePKFK)
+                return true;
+
+            return IsInvalidPKFKCatalog(catalogName) && IsInvalidPKFKCatalog(foreignCatalogName);
+        }
+
+        internal static string? BuildQualifiedTableName(string? catalogName, string? schemaName, string? tableName)
+        {
+            if (string.IsNullOrEmpty(tableName))
+                return tableName;
+
+            var parts = new System.Collections.Generic.List<string>();
+
+            if (!string.IsNullOrEmpty(schemaName))
+            {
+                if (!string.IsNullOrEmpty(catalogName) && !catalogName!.Equals("SPARK", StringComparison.OrdinalIgnoreCase))
+                {
+                    parts.Add($"`{catalogName.Replace("`", "``")}`");
+                }
+                parts.Add($"`{schemaName!.Replace("`", "``")}`");
+            }
+
+            parts.Add($"`{tableName!.Replace("`", "``")}`");
+
+            return string.Join(".", parts);
+        }
+    }
+}

csharp/src/MetadataUtilities.cs

@@ -25,6 +25,7 @@
 using System.Collections.Generic;
 using System.Text.Json.Serialization;
 using System.Text.RegularExpressions;
+using AdbcDrivers.HiveServer2.Hive2;
 using static AdbcDrivers.HiveServer2.Hive2.HiveServer2Connection;
 
 namespace AdbcDrivers.Databricks.Result
@@ -88,112 +89,38 @@ public ColumnTypeId DataType
             {
                 get
                 {
-                    string normalizedTypeName = Type.Name.Trim().ToUpper();
-
-                    return normalizedTypeName switch
-                    {
-                        "BOOLEAN" => ColumnTypeId.BOOLEAN,
-                        "TINYINT" or "BYTE" => ColumnTypeId.TINYINT,
-                        "SMALLINT" or "SHORT" => ColumnTypeId.SMALLINT,
-                        "INT" or "INTEGER" => ColumnTypeId.INTEGER,
-                        "BIGINT" or "LONG" => ColumnTypeId.BIGINT,
-                        "FLOAT" or "REAL" => ColumnTypeId.FLOAT,
-                        "DOUBLE" => ColumnTypeId.DOUBLE,
-                        "DECIMAL" or "NUMERIC" => ColumnTypeId.DECIMAL,
-
-                        "CHAR" => ColumnTypeId.CHAR,
-                        "STRING" or "VARCHAR" => ColumnTypeId.VARCHAR,
-                        "BINARY" => ColumnTypeId.BINARY,
-
-                        "TIMESTAMP" => ColumnTypeId.TIMESTAMP,
-                        "TIMESTAMP_LTZ" => ColumnTypeId.TIMESTAMP,
-                        "TIMESTAMP_NTZ" => ColumnTypeId.TIMESTAMP,
-                        "DATE" => ColumnTypeId.DATE,
-
-                        "ARRAY" => ColumnTypeId.ARRAY,
-                        "MAP" => ColumnTypeId.JAVA_OBJECT,
-                        "STRUCT" => ColumnTypeId.STRUCT,
-                        "INTERVAL" => ColumnTypeId.OTHER, // Intervals don't have a direct JDBC mapping
-                        "VOID" => ColumnTypeId.NULL,
-                        "VARIANT" => ColumnTypeId.OTHER,
-                        _ => ColumnTypeId.OTHER // Default fallback for unknown types
-                    };
+                    var code = (ColumnTypeId)ColumnMetadataHelper.GetDataTypeCode(Type.Name);
+                    // REAL maps to FLOAT for backward compatibility
+                    return code == ColumnTypeId.REAL ? ColumnTypeId.FLOAT : code;
                 }
             }
 
             [JsonIgnore]
-            public bool IsNumber
-            {
-                get
-                {
-                    return DataType switch
-                    {
-                        ColumnTypeId.TINYINT or ColumnTypeId.SMALLINT or ColumnTypeId.INTEGER or
-                        ColumnTypeId.BIGINT or ColumnTypeId.FLOAT or ColumnTypeId.DOUBLE or
-                        ColumnTypeId.DECIMAL or ColumnTypeId.NUMERIC => true,
-                        _ => false
-                    };
-                }
-            }
+            public bool IsNumber => ColumnMetadataHelper.GetNumPrecRadix(Type.Name) != null;
 
             [JsonIgnore]
-            public int DecimalDigits
-            {
-                get
-                {
-                    return DataType switch
-                    {
-                        ColumnTypeId.DECIMAL or ColumnTypeId.NUMERIC => Type.Scale ?? 0,
-                        ColumnTypeId.DOUBLE => 15,
-                        ColumnTypeId.FLOAT or ColumnTypeId.REAL => 7,
-                        ColumnTypeId.TIMESTAMP => 6,
-                        _ => 0
-                    };
-                }
-            }
+            public int DecimalDigits => ColumnMetadataHelper.GetDecimalDigitsDefault(Type.FullTypeName) ?? 0;
 
-            /// <summary>
-            /// Get column size
-            ///
-            /// Currently the query `DESC TABLE EXTNEDED AS JSON` does not return the column size,
-            /// we can calculate it based on the data type and some type specific properties
-            /// </summary>
             [JsonIgnore]
             public int? ColumnSize
             {
                 get
                 {
-                    return DataType switch
+                    // For INTERVAL types, FullTypeName may not include the qualifier
+                    // when only StartUnit is set. Use StartUnit directly in that case.
+                    if (Type.Name.Trim().Equals("INTERVAL", StringComparison.OrdinalIgnoreCase)
+                        && !string.IsNullOrEmpty(Type.StartUnit)
+                        && Type.EndUnit == null)
                     {
-                        ColumnTypeId.TINYINT or ColumnTypeId.BOOLEAN => 1,
-                        ColumnTypeId.SMALLINT => 2,
-                        ColumnTypeId.INTEGER or ColumnTypeId.FLOAT or ColumnTypeId.DATE => 4,
-                        ColumnTypeId.BIGINT or ColumnTypeId.DOUBLE or ColumnTypeId.TIMESTAMP or ColumnTypeId.TIMESTAMP_WITH_TIMEZONE => 8,
-                        ColumnTypeId.CHAR => Type.Length,
-                        ColumnTypeId.VARCHAR => Type.Name.Trim().ToUpper() == "STRING" ? int.MaxValue : Type.Length,
-                        ColumnTypeId.DECIMAL => Type.Precision ?? 0,
-                        ColumnTypeId.NULL => 1,
-                        _ => Type.Name.Trim().ToUpper() == "INTERVAL" ? GetIntervalSize() : 0
-                    };
-                }
-            }
-
-            private int GetIntervalSize()
-            {
-                if (String.IsNullOrEmpty(Type.StartUnit))
-                {
-                    return 0;
+                        return Type.StartUnit!.ToUpper() switch
+                        {
+                            "YEAR" or "MONTH" => 4,
+                            "DAY" or "HOUR" or "MINUTE" or "SECOND" => 8,
+                            _ => 4
+                        };
+                    }
+                    return ColumnMetadataHelper.GetColumnSizeDefault(Type.FullTypeName);
                 }
-
-                // Check whether interval is yearMonthIntervalQualifier or dayTimeIntervalQualifier
-                // yearMonthIntervalQualifier size is 4, dayTimeIntervalQualifier size is 8
-                // see https://docs.databricks.com/aws/en/sql/language-manual/data-types/interval-type
-                return Type.StartUnit!.ToUpper() switch
-                {
-                    "YEAR" or "MONTH" => 4,
-                    "DAY" or "HOUR" or "MINUTE" or "SECOND" => 8,
-                    _ => 4
-                };
             }
         }
 

csharp/src/Result/DescTableExtendedResult.cs

@@ -0,0 +1,98 @@
+/*
+ * 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 System.Text;
+
+namespace AdbcDrivers.Databricks.StatementExecution
+{
+    internal abstract class MetadataCommandBase
+    {
+        protected const string InAllCatalogs = " IN ALL CATALOGS";
+        protected const string LikeFormat = " LIKE '{0}'";
+        protected const string SchemaLikeFormat = " SCHEMA LIKE '{0}'";
+        protected const string TableLikeFormat = " TABLE LIKE '{0}'";
+        protected const string InCatalogFormat = " IN CATALOG {0}";
+        protected const string InSchemaFormat = " IN SCHEMA {0}";
+        protected const string InTableFormat = " IN TABLE {0}";
+
+        public abstract string Build();
+
+        protected static string QuoteIdentifier(string identifier)
+        {
+            return $"`{identifier.Replace("`", "``")}`";
+        }
+
+        protected static string ConvertPattern(string? pattern)
+        {
+            if (string.IsNullOrEmpty(pattern))
+                return "*";
+
+            var result = new StringBuilder(pattern!.Length);
+            bool escapeNext = false;
+
+            for (int i = 0; i < pattern.Length; i++)
+            {
+                char c = pattern[i];
+
+                if (c == '\\')
+                {
+                    if (i + 1 < pattern.Length && pattern[i + 1] == '\\')
+                    {
+                        result.Append("\\\\");
+                        i++;
+                    }
+                    else
+                    {
+                        escapeNext = !escapeNext;
+                        if (!escapeNext)
+                            result.Append('\\');
+                    }
+                }
+                else if (escapeNext)
+                {
+                    result.Append(c);
+                    escapeNext = false;
+                }
+                else if (c == '%')
+                {
+                    result.Append('*');
+                }
+                else if (c == '_')
+                {
+                    result.Append('.');
+                }
+                else if (c == '\'')
+                {
+                    result.Append("''");
+                }
+                else
+                {
+                    result.Append(c);
+                }
+            }
+
+            return result.ToString();
+        }
+
+        protected static void AppendCatalogScope(StringBuilder sql, string? catalog)
+        {
+            if (catalog == null)
+                sql.Append(InAllCatalogs);
+            else
+                sql.Append(string.Format(InCatalogFormat, QuoteIdentifier(catalog)));
+        }
+    }
+}

csharp/src/StatementExecution/MetadataCommandBase.cs

@@ -0,0 +1,38 @@
+/*
+ * 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 System.Text;
+
+namespace AdbcDrivers.Databricks.StatementExecution
+{
+    internal class ShowCatalogsCommand : MetadataCommandBase
+    {
+        private readonly string? _catalogPattern;
+
+        public ShowCatalogsCommand(string? catalogPattern = null)
+        {
+            _catalogPattern = catalogPattern;
+        }
+
+        public override string Build()
+        {
+            var sql = new StringBuilder("SHOW CATALOGS");
+            if (_catalogPattern != null)
+                sql.Append(string.Format(LikeFormat, ConvertPattern(_catalogPattern)));
+            return sql.ToString();
+        }
+    }
+}

csharp/src/StatementExecution/ShowCatalogsCommand.cs

@@ -0,0 +1,50 @@
+/*
+ * 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 System.Text;
+
+namespace AdbcDrivers.Databricks.StatementExecution
+{
+    internal class ShowColumnsCommand : MetadataCommandBase
+    {
+        private readonly string? _catalog;
+        private readonly string? _schemaPattern;
+        private readonly string? _tablePattern;
+        private readonly string? _columnPattern;
+
+        public ShowColumnsCommand(string? catalog, string? schemaPattern = null,
+            string? tablePattern = null, string? columnPattern = null)
+        {
+            _catalog = catalog;
+            _schemaPattern = schemaPattern;
+            _tablePattern = tablePattern;
+            _columnPattern = columnPattern;
+        }
+
+        public override string Build()
+        {
+            var sql = new StringBuilder("SHOW COLUMNS");
+            AppendCatalogScope(sql, _catalog);
+            if (_schemaPattern != null)
+                sql.Append(string.Format(SchemaLikeFormat, ConvertPattern(_schemaPattern)));
+            if (_tablePattern != null)
+                sql.Append(string.Format(TableLikeFormat, ConvertPattern(_tablePattern)));
+            if (_columnPattern != null && _columnPattern != "%")
+                sql.Append(string.Format(LikeFormat, ConvertPattern(_columnPattern)));
+            return sql.ToString();
+        }
+    }
+}