[improvement](information_schema)Support show default value in information_schema.

be/src/exec/schema_scanner/schema_columns_scanner.cpp

@@ -450,7 +450,19 @@ Status SchemaColumnsScanner::_fill_block_impl(vectorized::Block* block) {
         RETURN_IF_ERROR(fill_dest_column_for_range(block, 4, datas));
     }
     // COLUMN_DEFAULT
-    { RETURN_IF_ERROR(fill_dest_column_for_range(block, 5, null_datas)); }
+    {
+        std::vector<StringRef> strs(columns_num);
+        for (int i = 0; i < columns_num; ++i) {
+            if (_desc_result.columns[i].columnDesc.__isset.defaultValue) {
+                strs[i] = StringRef(_desc_result.columns[i].columnDesc.defaultValue.c_str(),
+                                    _desc_result.columns[i].columnDesc.defaultValue.length());
+                datas[i] = strs.data() + i;
+            } else {
+                datas[i] = nullptr;
+            }
+        }
+        RETURN_IF_ERROR(fill_dest_column_for_range(block, 5, datas));
+    }
     // IS_NULLABLE
     {
         StringRef str_yes = StringRef("YES", 3);

fe/fe-core/src/main/java/org/apache/doris/service/FrontendServiceImpl.java

@@ -971,6 +971,10 @@ private TColumnDesc getColumnDesc(Column column) {
             }
             desc.setChildren(children);
         }
+        String defaultValue = column.getDefaultValue();
+        if (defaultValue != null) {
+            desc.setDefaultValue(defaultValue);
+        }
         return desc;
     }
 

gensrc/thrift/FrontendService.thrift

@@ -53,6 +53,7 @@ struct TColumnDesc {
   6: optional bool isAllowNull
   7: optional string columnKey
   8: optional list<TColumnDesc> children
+  9: optional string defaultValue
 }
 
 // A column definition; used by CREATE TABLE and DESCRIBE <table> statements. A column

regression-test/data/account_p0/test_information_schema.out

@@ -17,3 +17,10 @@
 -- !sql --
 DUP
 
+-- !default --
+id	largeint	YES	\N
+name	varchar(20)	YES	无
+age	smallint(6)	YES	0
+address	varchar(100)	YES	beijing
+date	datetime	YES	20240101
+

regression-test/suites/account_p0/test_information_schema.groovy

@@ -87,4 +87,26 @@ suite("test_information_schema") {
         def dbName = dbPrefix + i.toString()
         sql "DROP DATABASE `${dbName}`"
     }
+
+    def dbName = dbPrefix + "default"
+    def tableName = tablePrefix + "default"
+    sql "CREATE DATABASE IF NOT EXISTS `${dbName}`"
+    sql "USE `${dbName}`"
+    sql """drop table if exists `${tableName}`"""
+    sql """
+        CREATE TABLE `${tableName}` (
+          `id` largeint NULL COMMENT '用户ID',
+          `name` varchar(20) NULL DEFAULT "无" COMMENT '用户姓名',
+          `age` smallint NULL DEFAULT "0" COMMENT '用户年龄',
+          `address` varchar(100) NULL DEFAULT "beijing" COMMENT '用户所在地区',
+          `date` datetime NULL DEFAULT "20240101" COMMENT '数据导入时间'
+        ) ENGINE=OLAP
+        DUPLICATE KEY(`id`, `name`)
+        DISTRIBUTED BY HASH(`id`) BUCKETS 1
+        PROPERTIES (
+        "replication_allocation" = "tag.location.default: 1")
+    """
+    qt_default "SELECT COLUMN_NAME as field,COLUMN_TYPE as type,IS_NULLABLE as isNullable, COLUMN_DEFAULT as defaultValue FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = '${tableName}' AND TABLE_SCHEMA = '${dbName}'"
+    sql "DROP DATABASE `${dbName}`"
 }
+