docs: add flush database doc

docs/en/12-taos-sql/02-database.md

@@ -179,6 +179,14 @@ TRIM DATABASE db_name;
 
 The preceding SQL statement deletes data that has expired and orders the remaining data in accordance with the storage configuration.
 
+## Flush Data
+
+```sql
+FLUSH DATABASE db_name;
+```
+
+Flush data from memory onto disk. Before shutting down a node, executing this command can avoid data restore after restarting and speed up the startup process.
+
 ## Redistribute Vgroup
 
 ```sql

docs/en/12-taos-sql/24-show.md

@@ -308,9 +308,11 @@ Query OK, 24 row(s) in set (0.002444s)
 </code></pre>
 </details>
 
-  The above show the block distribution percentage according to the number of rows in each block. In the above example, we can get below information:
-  - `_block_dist: 3483 |||||||||||||||||  1 (20.00%)` means there is one block whose rows is between 3,483 and 3,681.
-  -  `_block_dist: 3881 |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||  4 (80.00%)` means there are 4 blocks whose rows is between 3,881 and 4,096.   -  The number of blocks whose rows fall in other range is zero.
+The above show the block distribution percentage according to the number of rows in each block. In the above example, we can get below information:
+- `_block_dist: 3483 |||||||||||||||||  1 (20.00%)` means there is one block whose rows is between 3,483 and 3,681.
+-  `_block_dist: 3881 |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||  4 (80.00%)` means there are 4 blocks whose rows is between 3,881 and 4,096.   -  The number of blocks whose rows fall in other range is zero.
+
+Note that only the information about the data blocks in the data file will be displayed here, and the information about the data in the stt file will not be displayed.
 
 ## SHOW TAGS
 

docs/zh/12-taos-sql/02-database.md

@@ -179,6 +179,14 @@ TRIM DATABASE db_name;
 
 删除过期数据，并根据多级存储的配置归整数据。
 
+## 落盘内存数据
+
+```sql
+FLUSH DATABASE db_name;
+```
+
+落盘内存中的数据。在关闭节点之前，执行这条命令可以避免重启后的数据回放，加速启动过程。
+
 ## 调整VGROUP中VNODE的分布
 
 ```sql

docs/zh/12-taos-sql/24-show.md

@@ -253,8 +253,9 @@ Query OK, 24 row(s) in set (0.002444s)
 </code></pre>
  </details>
 
-  上面是块中包含数据行数的块儿分布情况图，这里的 0100 0299 0498 … 表示的是每个块中包含的数据行数，上面的意思就是这个表的 5 个块，分布在 3483 ~3681 行的块有 1 个，占整个块的 20%，分布在 3881 ~ 4096（最大行数）的块数为 4 个，占整个块的 80%， 其它区域内分布块数为 0。
+上面是块中包含数据行数的块儿分布情况图，这里的 0100 0299 0498 … 表示的是每个块中包含的数据行数，上面的意思就是这个表的 5 个块，分布在 3483 ~3681 行的块有 1 个，占整个块的 20%，分布在 3881 ~ 4096（最大行数）的块数为 4 个，占整个块的 80%， 其它区域内分布块数为 0。
 
+需要注意，这里只会显示 data 文件中数据块的信息，stt 文件中的数据的信息不会被显示。
 
 ## SHOW TAGS