dict_obj_tree 表提供了 dict_obj_info 表中表信息的树形视图。这主要用于测试，但可以用于可视化 NDB 数据库对象的层次结构。

dict_obj_tree 表包含以下列

path 列可用于在一行中获取给定 NDB 数据库对象的完整路径，而 indented_name 列可用于获取所需对象的完整层次结构信息的树形布局。

示例：假设存在一个 test 数据库，并且在该数据库中不存在名为 t1 的现有表，则执行以下 SQL 语句

CREATE TABLE test.t1 (
    a INT PRIMARY KEY,
    b INT,
    UNIQUE KEY(b)
)   ENGINE = NDB;

您可以使用此处显示的查询获取新创建表的路径

mysql> SELECT path FROM ndbinfo.dict_obj_tree
    -> WHERE name LIKE 'test%t1';
+-------------+
| path        |
+-------------+
| test/def/t1 |
+-------------+
1 row in set (0.14 sec)

您可以使用表的路径作为根名称，通过类似于此查询的方式查看该表的依赖对象路径

mysql> SELECT path FROM ndbinfo.dict_obj_tree
    -> WHERE root_name = 'test/def/t1';
+----------------------------------------------------------+
| path                                                     |
+----------------------------------------------------------+
| test/def/t1                                              |
| test/def/t1 -> sys/def/13/b                              |
| test/def/t1 -> sys/def/13/b -> NDB$INDEX_15_CUSTOM       |
| test/def/t1 -> sys/def/13/b$unique                       |
| test/def/t1 -> sys/def/13/b$unique -> NDB$INDEX_16_UI    |
| test/def/t1 -> sys/def/13/PRIMARY                        |
| test/def/t1 -> sys/def/13/PRIMARY -> NDB$INDEX_14_CUSTOM |
+----------------------------------------------------------+
7 rows in set (0.16 sec)

若要获取 t1 表及其所有依赖对象的层次结构视图，请执行类似于此查询的查询，该查询选择每个对象的缩进名称，其根对象名称为 test/def/t1

mysql> SELECT indented_name FROM ndbinfo.dict_obj_tree
    -> WHERE root_name = 'test/def/t1';
+----------------------------+
| indented_name              |
+----------------------------+
| test/def/t1                |
|   -> sys/def/13/b          |
|     -> NDB$INDEX_15_CUSTOM |
|   -> sys/def/13/b$unique   |
|     -> NDB$INDEX_16_UI     |
|   -> sys/def/13/PRIMARY    |
|     -> NDB$INDEX_14_CUSTOM |
+----------------------------+
7 rows in set (0.15 sec)

在使用磁盘数据表时，请注意，在此上下文中，表空间或日志文件组被视为根对象。这意味着您必须知道与给定表关联的任何表空间或日志文件组的名称，或者从 SHOW CREATE TABLE 中获取此信息，然后查询 INFORMATION_SCHEMA.FILES 或类似方法，如下所示

mysql> SHOW CREATE TABLE test.dt_1\G
*************************** 1. row ***************************
       Table: dt_1
Create Table: CREATE TABLE `dt_1` (
  `member_id` int unsigned NOT NULL AUTO_INCREMENT,
  `last_name` varchar(50) NOT NULL,
  `first_name` varchar(50) NOT NULL,
  `dob` date NOT NULL,
  `joined` date NOT NULL,
  PRIMARY KEY (`member_id`),
  KEY `last_name` (`last_name`,`first_name`)
) /*!50100 TABLESPACE `ts_1` STORAGE DISK */ ENGINE=ndbcluster DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci
1 row in set (0.00 sec)

mysql> SELECT DISTINCT TABLESPACE_NAME, LOGFILE_GROUP_NAME
    -> FROM INFORMATION_SCHEMA.FILES WHERE TABLESPACE_NAME='ts_1';
+-----------------+--------------------+
| TABLESPACE_NAME | LOGFILE_GROUP_NAME |
+-----------------+--------------------+
| ts_1            | lg_1               |
+-----------------+--------------------+
1 row in set (0.00 sec)

现在，您可以获取表、表空间和日志文件组的层次结构信息，如下所示

mysql> SELECT indented_name FROM ndbinfo.dict_obj_tree
    -> WHERE root_name = 'test/def/dt_1';
+----------------------------+
| indented_name              |
+----------------------------+
| test/def/dt_1              |
|   -> sys/def/23/last_name  |
|     -> NDB$INDEX_25_CUSTOM |
|   -> sys/def/23/PRIMARY    |
|     -> NDB$INDEX_24_CUSTOM |
+----------------------------+
5 rows in set (0.15 sec)

mysql> SELECT indented_name FROM ndbinfo.dict_obj_tree
    -> WHERE root_name = 'ts_1';
+-----------------+
| indented_name   |
+-----------------+
| ts_1            |
|   -> data_1.dat |
|   -> data_2.dat |
+-----------------+
3 rows in set (0.17 sec)

mysql> SELECT indented_name FROM ndbinfo.dict_obj_tree
    -> WHERE root_name LIKE 'lg_1';
+-----------------+
| indented_name   |
+-----------------+
| lg_1            |
|   -> undo_1.log |
|   -> undo_2.log |
+-----------------+
3 rows in set (0.16 sec)