Add doc to describe read-write split can not support transaction and … (#4533)

* Add doc to describe read-write split can not support transaction and explain the reason shortly #4455

* issues4533

docs/document/content/features/read-write-split/unsupported-items.cn.md

@@ -7,4 +7,5 @@ weight = 3
 
 1. 主库和从库的数据同步。
 1. 主库和从库的数据同步延迟导致的数据不一致。
-1. 主库双写或多写。
\ No newline at end of file
+1. 主库双写或多写。
+1. 跨主库和从库之间的事务的数据不一致。主从模型中，事务中读写均用主库。
\ No newline at end of file

docs/document/content/features/read-write-split/unsupported-items.en.md

@@ -8,3 +8,4 @@ weight = 3
 1. Data replication between the master and the slave database.
 1. Data inconsistency caused by replication delay between databases.
 1. Double or multiple master databases to provide write operation.
+1. The data for transaction across Master and Slave nodes are inconsitent. In the Master-Savle replication model, the master nodes need to be used for both reading and writing in the transaction.
\ No newline at end of file