Add CHAR and VARCHAR length support

Author: jackyhu-db

csharp/src/Drivers/Databricks/Result/DescTableExtendedResult.cs

@@ -150,6 +150,8 @@ public int? ColumnSize
                         ColumnTypeId.SMALLINT => 2,
                         ColumnTypeId.INTEGER or ColumnTypeId.FLOAT or ColumnTypeId.DATE => 4,
                         ColumnTypeId.BIGINT or ColumnTypeId.DECIMAL or ColumnTypeId.DOUBLE or ColumnTypeId.TIMESTAMP or ColumnTypeId.TIMESTAMP_WITH_TIMEZONE => 8,
+                        ColumnTypeId.CHAR => Type.Length,
+                        ColumnTypeId.VARCHAR => Type.Name.Trim().ToUpper() == "STRING" ? null: Type.Length,
                         _ => null
                     };
                 }
@@ -171,30 +173,60 @@ internal class ColumnType
             [JsonPropertyName("name")]
             public string Name { get; set; } = String.Empty;
 
+            /// <summary>
+            /// Precision for DECIMAL type, only for DECIMAL and NUMERIC types
+            /// </summary>
             [JsonPropertyName("precision")]
             public int? Precision { get; set; }
 
+            /// <summary>
+            /// Scale for DECIMAL type, only for DECIMAL and NUMERIC types
+            /// </summary>
             [JsonPropertyName("scale")]
             public int? Scale { get; set; }
 
+            /// <summary>
+            /// Element type for ARRAY type, only for ARRAY type
+            /// </summary>
             [JsonPropertyName("element_type")]
             public ColumnType? ElementType { get; set; }
 
+            /// <summary>
+            /// Key and value types for MAP type, only for MAP type
+            /// </summary>
             [JsonPropertyName("key_type")]
             public ColumnType? KeyType { get; set; }
 
+            /// <summary>
+            /// Value type for MAP type, only for MAP type
+            /// </summary>
             [JsonPropertyName("value_type")]
             public ColumnType? ValueType { get; set; }
 
+            /// <summary>
+            /// Fields for STRUCT type, only for STRUCT type
+            /// </summary>
             [JsonPropertyName("fields")]
             public List<ColumnInfo>? Fields { get; set; }
 
+            /// <summary>
+            /// Interval start and end units, only for INTERVAL type
+            /// </summary>
             [JsonPropertyName("start_unit")]
             public string? StartUnit { get; set; }
 
+            /// <summary>
+            /// Interval start and end units, only for INTERVAL type
+            /// </summary>
             [JsonPropertyName("end_unit")]
             public string? EndUnit { get; set; }
 
+            /// <summary>
+            /// Length of characters, only for character types (CHAR, VARCHAR)
+            /// </summary>
+            [JsonPropertyName("length")]
+            public int? Length {get; set; }
+
             /// <summary>
             /// Get the full type name e.g. DECIMAL(10,2), map<string,int>
             /// </summary>
@@ -207,6 +239,7 @@ public string FullTypeName
 
                     return normalizedTypeName switch
                     {
+                        "CHAR" or "VARCHAR" => $"{normalizedTypeName}({Length ?? 1})",
                         "DECIMAL" or "NUMERIC" => Precision != null ? $"{normalizedTypeName}({Precision},{Scale ?? 0})" : normalizedTypeName,
                         "ARRAY" => ElementType != null ? $"ARRAY<{ElementType.FullTypeName}>" : "ARRAY<>",
                         "MAP" => (KeyType != null && ValueType != null) ? $"MAP<{KeyType!.FullTypeName},{ValueType!.FullTypeName}>":"Map<>",

csharp/test/Drivers/Databricks/Result/DescTableExtendedResultTest.cs

@@ -52,13 +52,29 @@ public void TestTableWithoutConstraints()
                         ""nullable"": false
                     },
                     {
-                        ""name"": ""string_col"",
+                    ""name"": ""string_col"",
                         ""type"": {
                             ""name"": ""string"",
                             ""collation"": ""UTF8_BINARY""
                         },
                         ""nullable"": false
                     },
+                    {
+                        ""name"": ""varchar_col"",
+                        ""type"": {
+                            ""name"": ""varchar"",
+                            ""length"": 20
+                        },
+                        ""nullable"": false
+                    },
+                    {
+                        ""name"": ""char_col"",
+                        ""type"": {
+                            ""name"": ""char"",
+                            ""length"": 20
+                        },
+                        ""nullable"": false
+                    },
                     {
                         ""name"": ""array_col"",
                         ""type"": {
@@ -149,7 +165,7 @@ public void TestTableWithoutConstraints()
             Assert.Empty(result.PrimaryKeys);
             Assert.Empty(result.ForeignKeys);
 
-            Assert.Equal(7, result.Columns.Count);
+            Assert.Equal(9, result.Columns.Count);
 
             var column = result.Columns.Find(c => c.Name == "big_number");
             Assert.NotNull(column);
@@ -171,6 +187,18 @@ public void TestTableWithoutConstraints()
             Assert.Equal("string", column.Type.Name);
             Assert.Equal("STRING", column.Type.FullTypeName);
 
+            column = result.Columns.Find(c => c.Name == "varchar_col");
+            Assert.NotNull(column);
+            Assert.Equal("varchar", column.Type.Name);
+            Assert.Equal(20, column.Type.Length);
+            Assert.Equal("VARCHAR(20)", column.Type.FullTypeName);
+
+            column = result.Columns.Find(c => c.Name == "char_col");
+            Assert.NotNull(column);
+            Assert.Equal("char", column.Type.Name);
+            Assert.Equal(20, column.Type.Length);
+            Assert.Equal("CHAR(20)", column.Type.FullTypeName);
+
             column = result.Columns.Find(c => c.Name == "array_col");
             Assert.NotNull(column);
             Assert.Equal("array", column.Type.Name);
@@ -309,8 +337,8 @@ public void TestTableWithConstraints(string constaints, string[] primaryKeys, st
         [InlineData("REAL", ColumnTypeId.FLOAT, true, 4)]
         [InlineData("DOUBLE", ColumnTypeId.DOUBLE, true, 8)]
         [InlineData("DECIMAL", ColumnTypeId.DECIMAL, true, 8)]
-        [InlineData("CHAR", ColumnTypeId.CHAR, false, null)]
-        [InlineData("VARCHAR", ColumnTypeId.VARCHAR, false, null)]
+        [InlineData("CHAR", ColumnTypeId.CHAR, false, 20)]
+        [InlineData("VARCHAR", ColumnTypeId.VARCHAR, false, 20)]
         [InlineData("STRING", ColumnTypeId.VARCHAR, false, null)]
         [InlineData("BINARY", ColumnTypeId.BINARY,false, null )]
         [InlineData("DATE", ColumnTypeId.DATE, false, 4)]
@@ -334,7 +362,8 @@ internal void TestCalculatedTypeProperties(string baseType, ColumnTypeId dataTyp
                     {
                         ""name"": ""col"",
                         ""type"": {
-                            ""name"": ""<col_type>""
+                            ""name"": ""<col_type>"",
+                            ""length"": 20
                         },
                         ""nullable"": false
                     }