# 创建和卸载IMCV
#### 普通表创建IMCV
- 语法
  - HTAP可以通过ALTER方式对普通表创建IMCV，如[表1]所示。
    详情请参见《参考》中"SQL参考 \> SQL语法 \> A \> ALTER TABLE"章节。
     表1ALTER方式创建IMCV语法和相关影响 
    | 语法                                          | 加载列              |
    |:---|:---|
    | ALTER TABLE ... COLVIEW                     | 全部列。             |
    | ALTER TABLE ... NOCOLVIEW                   | 无，IMCV信息被删除。     |
    | ALTER TABLE ... NOCOLVIEW COLVIEW(col_list) | col_list中全部列。    |
    | ALTER TABLE ... COLVIEW NOCOLVIEW(col_list) | 不在col_list中的其他列。 |
       
    
  
  
  
  - HTAP可以通过CREATE方式对普通表创建IMCV，创建普通表时可以指定表级IMCV或者列级IMCV。 详情请参见《参考》中"SQL参考 \> SQL语法 \> C \> CREATE TABLE"章节。
    表级IMCV和列级IMCV互相影响决定最终加载哪些IMCV列。表级和列级IMCV关键字的影响关系如[表2]所示。
     表2表级和列级IMCV关键字影响关系 
    | **表级IMCV关键字** | **列级IMCV关键字**       | 最终加载列              |
    |:---|:---|:---|
    | COLVIEW       | 无/COLVIEW           | 全部列。               |
    | COLVIEW       | 无/COLVIEW/NOCOLVIEW | 除定义NOCOLVIEW外的其他列。 |
    | NOCOLVIEW/无   | 无/COLVIEW/NOCOLVIEW | 定义了COLVIEW的列。      |
       
    
   

- 示例
  - 通过ALTER方式创建IMCV。
    ```
    --创建普通表htap_test并插入数据。
    htapdb=# CREATE TABLE htap_test(
              id int,
              dept_id int,
              salary int,
              name varchar(20),
              comments varchar(30)) with (storage_type = ustore) distribute by hash(id);
    CREATE TABLE
    htapdb=# INSERT INTO htap_test VALUES (generate_series(1,100), 1, 8000, 'Allen', 'For test');
    INSERT 0 100
    --建表插入数据后执行ALTER COLVIEW创建IMCV。
    htapdb=# ALTER TABLE htap_test COLVIEW;
    ALTER TABLE
    htapdb=# SELECT total FROM gs_imcv_flush('htap_test');
     total 
    -------
     2
    (1 row)
    htapdb=# SELECT node_name, rel_name, imcvnattr, imcvkey, rowgroup_num, cu_num_in_mem, cu_mem_size, cu_num_in_disk, cu_disk_size FROM gs_global_imcv_info() ORDER BY node_name,rel_name;
      node_name   | rel_name  | imcvnattr |  imcvkey  | rowgroup_num | cu_num_in_mem | cu_mem_size | cu_num_in_disk | cu_disk_size 
    --------------+-----------+-----------+-----------+--------------+---------------+-------------+----------------+--------------
     dn_6001_6002 | htap_test |         5 | 1 2 3 4 5 |            1 |             6 |        8153 |              0 |            0
     dn_6003_6004 | htap_test |         5 | 1 2 3 4 5 |            1 |             6 |        8185 |              0 |            0
    (2 rows)
    --卸载IMCV。
    htapdb=# ALTER TABLE htap_test NOCOLVIEW;
    ALTER TABLE
    htapdb=# SELECT node_name, rel_name, imcvnattr, imcvkey, rowgroup_num, cu_num_in_mem, cu_mem_size, cu_num_in_disk, cu_disk_size FROM gs_global_imcv_info() ORDER BY node_name,rel_name;
     node_name | rel_name | imcvnattr | imcvkey | rowgroup_num | cu_num_in_mem | cu_mem_size | cu_num_in_disk | cu_disk_size 
    -----------+----------+-----------+---------+--------------+---------------+-------------+----------------+--------------
    (0 rows)
    --加载除dept_id/comments外的其他列。
    htapdb=# ALTER TABLE htap_test COLVIEW NOCOLVIEW(dept_id, comments);
    ALTER TABLE
    htapdb=# SELECT node_name, rel_name, imcvnattr, imcvkey, rowgroup_num, cu_num_in_mem, cu_mem_size, cu_num_in_disk, cu_disk_size FROM gs_global_imcv_info() ORDER BY node_name,rel_name;
      node_name   | rel_name  | imcvnattr | imcvkey | rowgroup_num | cu_num_in_mem | cu_mem_size | cu_num_in_disk | cu_disk_size 
    --------------+-----------+-----------+---------+--------------+---------------+-------------+----------------+--------------
     dn_6001_6002 | htap_test |         3 | 1 3 4   |            1 |             4 |        8153 |              0 |            0
     dn_6003_6004 | htap_test |         3 | 1 3 4   |            1 |             4 |        8185 |              0 |            0
    (2 rows)
    --卸载IMCV。
    htapdb=# ALTER TABLE htap_test NOCOLVIEW;
    ALTER TABLE
    --加载id/name列。
    htapdb=# ALTER TABLE htap_test NOCOLVIEW COLVIEW(id, name);
    ALTER TABLE
    htapdb=# SELECT node_name, rel_name, imcvnattr, imcvkey, rowgroup_num, cu_num_in_mem, cu_mem_size, cu_num_in_disk, cu_disk_size FROM gs_global_imcv_info() ORDER BY node_name,rel_name;
      node_name   | rel_name  | imcvnattr | imcvkey | rowgroup_num | cu_num_in_mem | cu_mem_size | cu_num_in_disk | cu_disk_size 
    --------------+-----------+-----------+---------+--------------+---------------+-------------+----------------+--------------
     dn_6001_6002 | htap_test |         2 | 1 4     |            1 |             3 |        8153 |              0 |            0
     dn_6003_6004 | htap_test |         2 | 1 4     |            1 |             3 |        8185 |              0 |            0
    (2 rows)
    htapdb=# DROP TABLE htap_test;
    DROP TABLE
    ```
    ![](https://support.huaweicloud.com/distributed-devg-v10-gaussdb/public_sys-resources/note_3.0-zh-cn.png)
    gs_imcv是HTAP相关的共享系统表，详情请参见《参考》中"系统表和系统视图 \> 系统表 \> HTAP \> GS_IMCV"章节。
    
  
  
  
  - 建表时指定表级IMCV关键字为COLVIEW，不指定列级IMCV关键字。
    ```
    htapdb=# CREATE TABLE htap_test(
              id int,
              dept_id int,
              salary int,
              name varchar(20),
              comments varchar(30)) COLVIEW with (storage_type = ustore) distribute by hash(id);
    CREATE TABLE
    --查询系统表gs_imcv，表的全部列均加载IMCV。
    htapdb=# SELECT relname,imcvkey FROM gs_imcv;
      relname  |  imcvkey  
    -----------+-----------
     htap_test | 1 2 3 4 5
    (1 row)
    htapdb=# DROP TABLE htap_test;
    DROP TABLE
    ```
    
  
  - 建表时指定表级IMCV关键字为COLVIEW，指定部分列级IMCV关键字为NOCOLVIEW，其余列不指定IMCV关键字。
    ```
    htapdb=#  CREATE TABLE htap_test(
              id int,
              dept_id int NOCOLVIEW,
              salary int,
              name varchar(20) NOCOLVIEW,
              comments varchar(30)) COLVIEW WITH (storage_type = ustore) DISTRIBUTE BY HASH(id);
    CREATE TABLE
    --查询系统表gs_imcv，列id、salary和comments加载IMCV。
    htapdb=# SELECT relname,imcvkey FROM gs_imcv;
      relname  | imcvkey 
    -----------+---------
     htap_test | 1 3 5
    (1 row)
    htapdb=# DROP TABLE htap_test;
    DROP TABLE
    ```
    
  
  - 建表时不指定表级IMCV关键字，部分列指定IMCV关键字为COLVIEW，其余列不指定IMCV关键字。
    ```
    htapdb=# CREATE TABLE htap_test(
              id int COLVIEW,
              dept_id int,
              salary int,
              name varchar(20) COLVIEW,
              comments varchar(30)) WITH (storage_type = ustore) DISTRIBUTE BY HASH(id);
    CREATE TABLE
    --查询系统表gs_imcv，列id、name加载IMCV。
    htapdb=# SELECT relname,imcvkey FROM gs_imcv;
      relname  | imcvkey 
    -----------+---------
     htap_test | 1 4
    (1 row)
    htapdb=# DROP TABLE htap_test;
    DROP TABLE
    ```
    
   
 
#### 分区表创建IMCV
- 语法
  - HTAP可以通过ALTER方式对分区表创建IMCV，分区表ALTER方式创建IMCV继承普通表的用法。对分区表额外增加对分区的ALTER语法，如下所示：
    ```
    ALTER TABLE table_name MODIFY PARTITION part_name COLVIEW;
    ```
    
  
  
  详情请参见《参考》中"SQL参考 \> SQL语法 \> A \> ALTER TABLE"章节。
  - HTAP可以通过CREATE方式对分区表创建IMCV，创建分区表时可以指定表级IMCV、列级IMCV或分区级IMCV。 具体语法请参见《参考》中"SQL参考 \> SQL语法 \> C \> CREATE TABLE"章节
    分区表的IMCV加载列同样由表级IMCV和列级IMCV决定，规则与普通表一致。分区表有分区级IMCV，分区级IMCV和表级IMCV互相影响，决定最终有哪些分区加载IMCV。分区的IMCV列信息和基表保持一致。表级IMCV和分区级IMCV关键字的影响关系如[表3]所示。
     表3表级和分区级IMCV关键字影响关系 
    | 表级IMCV关键字           | 分区IMCV关键字 | 分区是否创建IMCV |
    |:---|:---|:---|
    | COLVIEW             | 无/COLVIEW | 是          |
    | 无/COLVIEW/NOCOLVIEW | NOCOLVIEW | 否          |
    | 无/NOCOLVIEW         | COLVIEW   | 是          |
       
    
   
- 示例
  - 指定分区加载IMCV。
    ```
    --创建分区表htap_test并插入数据。
    htapdb=# CREATE TABLE htap_test(
              id int,
              dept_id int,
              salary int,
              name varchar(20),
              comments varchar(30)
              ) WITH(storage_type = ustore) DISTRIBUTE BY HASH(id)
              PARTITION BY HASH (id)(
              PARTITION id_p1,
              PARTITION id_p2,
              PARTITION id_p3);
    CREATE TABLE
    htapdb=# INSERT INTO htap_test VALUES (generate_series(1,100), 1, 8000, 'Allen', 'For test');
    INSERT 0 100
    --表htap_test没有加载IMCV，系统表gs_imcv查询记录为空。
    htapdb=# SELECT relname,imcvkey FROM gs_imcv;
     relname | imcvkey 
    ---------+---------
    (0 rows)
    --通过ALTER为指定分区id_p1加载IMCV。
    htapdb=# ALTER TABLE htap_test MODIFY PARTITION id_p1 COLVIEW;
    ALTER TABLE
    htapdb=# SELECT node_name, rel_name, partition_name, imcvnattr, imcvkey, rowgroup_num, cu_num_in_mem, cu_mem_size, cu_num_in_disk, cu_disk_size FROM gs_global_imcv_info() ORDER BY node_name, rel_name;
      node_name   | rel_name  | partition_name | imcvnattr |  imcvkey  | rowgroup_num | cu_num_in_mem | cu_mem_size | cu_num_in_disk | cu_disk_size 
    --------------+-----------+----------------+-----------+-----------+--------------+---------------+-------------+----------------+--------------
     dn_6001_6002 | htap_test | id_p1          |         5 | 1 2 3 4 5 |            1 |             6 |        8101 |              0 |            0
     dn_6001_6002 | htap_test |                |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
     dn_6003_6004 | htap_test | id_p1          |         5 | 1 2 3 4 5 |            1 |             6 |        8101 |              0 |            0
     dn_6003_6004 | htap_test |                |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
    (4 rows)
    htapdb=# DROP TABLE htap_test;
    DROP TABLE
    ```
    
  
  - 创建分区表时指定表级IMCV关键字为COLVIEW，不指定分区级IMCV关键字。
    ```
    htapdb=# CREATE TABLE htap_test(
              id int,
              dept_id int,
              salary int,
              name varchar(20),
              comments varchar(30)
              ) COLVIEW WITH(storage_type = ustore) DISTRIBUTE BY HASH(id)
              PARTITION BY HASH (id)(
              PARTITION id_p1,
              PARTITION id_p2,
              PARTITION id_p3);
    CREATE TABLE
    --所有分区均加载IMCV。
    htapdb=# SELECT node_name, rel_name, partition_name, imcvnattr, imcvkey, rowgroup_num, cu_num_in_mem, cu_mem_size, cu_num_in_disk, cu_disk_size FROM gs_global_imcv_info() ORDER BY node_name,rel_name;
      node_name   | rel_name  | partition_name | imcvnattr |  imcvkey  | rowgroup_num | cu_num_in_mem | cu_mem_size | cu_num_in_disk | cu_disk_size 
    --------------+-----------+----------------+-----------+-----------+--------------+---------------+-------------+----------------+--------------
     dn_6001_6002 | htap_test | id_p1          |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
     dn_6001_6002 | htap_test | id_p2          |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
     dn_6001_6002 | htap_test | id_p3          |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
     dn_6001_6002 | htap_test |                |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
     dn_6003_6004 | htap_test | id_p1          |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
     dn_6003_6004 | htap_test | id_p2          |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
     dn_6003_6004 | htap_test | id_p3          |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
     dn_6003_6004 | htap_test |                |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
    (8 rows)
    htapdb=# DROP TABLE htap_test;
    DROP TABLE
    ```
    
  
  - 创建分区表时指定表级IMCV关键字为COLVIEW，指定部分分区IMCV关键字为NOCOLVIEW。
    ```
    htapdb=# CREATE TABLE htap_test(
              id int,
              dept_id int,
              salary int,
              name varchar(20),
              comments varchar(30)
              ) COLVIEW WITH(storage_type = ustore) DISTRIBUTE BY HASH(id)
              PARTITION BY HASH (id)(
              PARTITION id_p1,
              PARTITION id_p2 NOCOLVIEW,
              PARTITION id_p3 );
    CREATE TABLE
    --除id_p2外的其他分区均加载IMCV。
    htapdb=# SELECT node_name, rel_name, partition_name, imcvnattr, imcvkey, rowgroup_num, cu_num_in_mem, cu_mem_size, cu_num_in_disk, cu_disk_size FROM gs_global_imcv_info() ORDER BY node_name,rel_name;
      node_name   | rel_name  | partition_name | imcvnattr |  imcvkey  | rowgroup_num | cu_num_in_mem | cu_mem_size | cu_num_in_disk | cu_disk_size 
    --------------+-----------+----------------+-----------+-----------+--------------+---------------+-------------+----------------+--------------
     dn_6001_6002 | htap_test | id_p1          |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
     dn_6001_6002 | htap_test | id_p3          |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
     dn_6001_6002 | htap_test |                |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
     dn_6003_6004 | htap_test | id_p1          |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
     dn_6003_6004 | htap_test | id_p3          |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
     dn_6003_6004 | htap_test |                |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
    (6 rows)
    htapdb=# DROP TABLE htap_test;
    DROP TABLE
    ```
    
  
  
  
  - 创建分区表时指定表级IMCV关键字为NOCOLVIEW，指定部分分区IMCV关键字为COLVIEW。
    ```
    --一级分区。
    htapdb=# CREATE TABLE htap_test(
              id int,
              dept_id int,
              salary int,
              name varchar(20),
              comments varchar(30)
              ) NOCOLVIEW WITH(storage_type = ustore) DISTRIBUTE BY HASH(id)
              PARTITION BY HASH (id)(
              PARTITION id_p1,
              PARTITION id_p2 COLVIEW,
              PARTITION id_p3 );
    CREATE TABLE
    --分区id_p2加载IMCV，其余分区不加载IMCV。
    htapdb=# SELECT node_name, rel_name, partition_name, imcvnattr, imcvkey, rowgroup_num, cu_num_in_mem, cu_mem_size, cu_num_in_disk, cu_disk_size FROM gs_global_imcv_info() ORDER BY node_name,rel_name;
      node_name   | rel_name  | partition_name | imcvnattr |  imcvkey  | rowgroup_num | cu_num_in_mem | cu_mem_size | cu_num_in_disk | cu_disk_size 
    --------------+-----------+----------------+-----------+-----------+--------------+---------------+-------------+----------------+--------------
     dn_6001_6002 | htap_test | id_p2          |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
     dn_6001_6002 | htap_test |                |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
     dn_6003_6004 | htap_test | id_p2          |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
     dn_6003_6004 | htap_test |                |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
    (4 rows)
    htapdb=# DROP TABLE htap_test;
    DROP TABLE
    ```
    
   
 
#### 普通表卸载IMCV
- 语法
  通过ALTER语句删除IMCV列存数据并删除IMCV元信息。
  ```
  ALTER TABLE table_name NOCOLVIEW;
  ```
  
- 示例
  ALTER TABLE ... NOCOLVIEW方式删除IMCV。
  ```
  htapdb=# CREATE TABLE htap_test(
            id int,
            dept_id int,
            salary int,
            name varchar(20),
            comments varchar(30)) COLVIEW WITH (storage_type = ustore) DISTRIBUTE BY HASH(id);
  CREATE TABLE
  htapdb=# SELECT node_name, rel_name, partition_name, imcvnattr, imcvkey, rowgroup_num, cu_num_in_mem, cu_mem_size, cu_num_in_disk, cu_disk_size FROM gs_global_imcv_info() ORDER BY node_name,rel_name;
    node_name   | rel_name  | partition_name | imcvnattr |  imcvkey  | rowgroup_num | cu_num_in_mem | cu_mem_size | cu_num_in_disk | cu_disk_size 
  --------------+-----------+----------------+-----------+-----------+--------------+---------------+-------------+----------------+--------------
   dn_6001_6002 | htap_test |                |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
   dn_6003_6004 | htap_test |                |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
  (2 rows)
  htapdb=# ALTER TABLE htap_test NOCOLVIEW;
  ALTER TABLE
  --删除IMCV后，系统函数gs_global_imcv_info()查询无记录。
  htapdb=# SELECT node_name, rel_name, partition_name, imcvnattr, imcvkey, rowgroup_num, cu_num_in_mem, cu_mem_size, cu_num_in_disk, cu_disk_size FROM gs_global_imcv_info() ORDER BY node_name,rel_name;
   node_name | rel_name | partition_name | imcvnattr | imcvkey | rowgroup_num | cu_num_in_mem | cu_mem_size | cu_num_in_disk | cu_disk_size 
  -----------+----------+----------------+-----------+---------+--------------+---------------+-------------+----------------+--------------
  (0 rows)
  htapdb=# DROP TABLE htap_test;
  DROP TABLE
  ```
  
 
#### 分区表卸载IMCV
- 语法 分区表继承普通表删除IMCV的方式，并且可以针对分区删除IMCV列存数据和IMCV元信息。
  ```
  ALTER TABLE table_name MODIFY PARTITION part_name NOCOLVIEW;
  ```
  

- 示例
  对分区表删除IMCV。
  ```
  htapdb=# CREATE TABLE htap_test(
            id int,
            dept_id int,
            salary int,
            name varchar(20),
            comments varchar(30)
   ) WITH (storage_type = ustore) DISTRIBUTE BY HASH(id)
   PARTITION BY RANGE (id)
   (
    PARTITION id_p1 VALUES LESS THAN (100),
    PARTITION id_p2 VALUES LESS THAN (200) COLVIEW,
    PARTITION id_p3 VALUES LESS THAN (300) COLVIEW,
    PARTITION id_p4 VALUES LESS THAN (400) ,
    PARTITION id_p5 VALUES LESS THAN (MAXVALUE));
  CREATE TABLE
  htapdb=# SELECT node_name, rel_name, partition_name, imcvnattr, imcvkey, rowgroup_num, cu_num_in_mem, cu_mem_size, cu_num_in_disk, cu_disk_size FROM gs_global_imcv_info() ORDER BY node_name,rel_name;
    node_name   | rel_name  | partition_name | imcvnattr |  imcvkey  | rowgroup_num | cu_num_in_mem | cu_mem_size | cu_num_in_disk | cu_disk_size 
  --------------+-----------+----------------+-----------+-----------+--------------+---------------+-------------+----------------+--------------
   dn_6001_6002 | htap_test | id_p3          |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
   dn_6001_6002 | htap_test |                |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
   dn_6001_6002 | htap_test | id_p2          |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
   dn_6003_6004 | htap_test | id_p3          |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
   dn_6003_6004 | htap_test |                |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
   dn_6003_6004 | htap_test | id_p2          |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
  (6 rows)
  htapdb=# ALTER TABLE htap_test MODIFY PARTITION id_p2 NOCOLVIEW;
  ALTER TABLE
  htapdb=# SELECT node_name, rel_name, partition_name, imcvnattr, imcvkey, rowgroup_num, cu_num_in_mem, cu_mem_size, cu_num_in_disk, cu_disk_size FROM gs_global_imcv_info() ORDER BY node_name,rel_name;
    node_name   | rel_name  | partition_name | imcvnattr |  imcvkey  | rowgroup_num | cu_num_in_mem | cu_mem_size | cu_num_in_disk | cu_disk_size 
  --------------+-----------+----------------+-----------+-----------+--------------+---------------+-------------+----------------+--------------
   dn_6001_6002 | htap_test | id_p3          |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
   dn_6001_6002 | htap_test |                |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
   dn_6003_6004 | htap_test | id_p3          |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
   dn_6003_6004 | htap_test |                |         5 | 1 2 3 4 5 |            0 |             0 |           0 |              0 |            0
  (4 rows)
  htapdb=# ALTER TABLE htap_test DROP PARTITION id_p3;
  ALTER TABLE
  htapdb=# SELECT node_name, rel_name, partition_name, imcvnattr, imcvkey, rowgroup_num, cu_num_in_mem, cu_mem_size, cu_num_in_disk, cu_disk_size FROM gs_global_imcv_info() ORDER BY node_name,rel_name;
   node_name | rel_name | partition_name | imcvnattr | imcvkey | rowgroup_num | cu_num_in_mem | cu_mem_size | cu_num_in_disk | cu_disk_size 
  -----------+----------+----------------+-----------+---------+--------------+---------------+-------------+----------------+--------------
  (0 rows)
  htapdb=# DROP TABLE htap_test;
  DROP TABLE
  ```