[iotdb] branch rel/0.12 updated: add doc for flush command

[qi...@apache.org]

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qiaojialin pushed a commit to branch rel/0.12
in repository https://gitbox.apache.org/repos/asf/iotdb.git


The following commit(s) were added to refs/heads/rel/0.12 by this push:
     new be9f0c1  add doc for flush command
be9f0c1 is described below

commit be9f0c19eb8262e15e7ec8b3f49e69b6179808e4
Author: qiaojialin <64...@qq.com>
AuthorDate: Tue Nov 23 08:57:34 2021 +0800

    add doc for flush command
---
 docs/UserGuide/IoTDB-SQL-Language/Maintenance-Command.md    | 4 ++++
 docs/zh/UserGuide/IoTDB-SQL-Language/Maintenance-Command.md | 3 +++
 2 files changed, 7 insertions(+)

diff --git a/docs/UserGuide/IoTDB-SQL-Language/Maintenance-Command.md b/docs/UserGuide/IoTDB-SQL-Language/Maintenance-Command.md
index 8886254..80ecbc6 100644
--- a/docs/UserGuide/IoTDB-SQL-Language/Maintenance-Command.md
+++ b/docs/UserGuide/IoTDB-SQL-Language/Maintenance-Command.md
@@ -23,6 +23,10 @@
 
 Persist all the data points in the memory table of the storage group to the disk, and seal the data file.
 
+Note: This command does not need to be invoked manually by the client. IoTDB has WAL to ensure data security 
+and IoTDB will flush when appropriate.
+Frequently call flush can result in small data files that degrade query performance.
+
 ```sql
 IoTDB> FLUSH 
 IoTDB> FLUSH root.ln
diff --git a/docs/zh/UserGuide/IoTDB-SQL-Language/Maintenance-Command.md b/docs/zh/UserGuide/IoTDB-SQL-Language/Maintenance-Command.md
index fc08eef..bc995d2 100644
--- a/docs/zh/UserGuide/IoTDB-SQL-Language/Maintenance-Command.md
+++ b/docs/zh/UserGuide/IoTDB-SQL-Language/Maintenance-Command.md
@@ -24,6 +24,9 @@
 
 将指定存储组的内存缓存区Memory Table的数据持久化到磁盘上，并将数据文件封口。
 
+注意：此命令客户端不需要手动调用，IoTDB 有 wal 保证数据安全，IoTDB 会选择合适的时机进行 flush。
+如果频繁调用 flush 会导致数据文件很小，降低查询性能。
+
 ```sql
 IoTDB> FLUSH 
 IoTDB> FLUSH root.ln