[iotdb] 01/01: add description for flush command

[qi...@apache.org]

This is an automated email from the ASF dual-hosted git repository.

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

commit 86a425f2b245159f31400cf59c949c799ac422b3
Author: qiaojialin <64...@qq.com>
AuthorDate: Tue Nov 23 08:59:08 2021 +0800

    add description 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 12e9b3d..6dc104f 100644
--- a/docs/UserGuide/IoTDB-SQL-Language/Maintenance-Command.md
+++ b/docs/UserGuide/IoTDB-SQL-Language/Maintenance-Command.md
@@ -24,6 +24,10 @@
 
 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 a20ec7e..e6c422a 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