From f99bd6e2dde2902a2d0abaa10b9a01178cdfc77b Mon Sep 17 00:00:00 2001
From: TomShawn <1135243111@qq.com>
Date: Tue, 14 Apr 2020 19:38:47 +0800
Subject: [PATCH] reference/transaction: add a description

---
 reference/transactions/overview.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/reference/transactions/overview.md b/reference/transactions/overview.md
index 1f6a32f55df91..67850936b092c 100644
--- a/reference/transactions/overview.md
+++ b/reference/transactions/overview.md
@@ -202,3 +202,5 @@ Therefore, TiDB intentionally imposes some limits on transaction sizes:
 For each transaction, it is recommended to keep the number of SQL statements between 100 to 500 to achieve an optimal performance.
 
 TiDB sets a default limit of 100 MB for the total size of key-value pairs, which can be modified by the `txn-total-size-limit` configuration item in the configuration file. The maximum value of `txn-total-size-limit` is 10 GB. The actual size limit of one transaction also depends on the memory capacity. When executing large transactions, the memory usage of the TiDB process is approximately 6 times larger than the total size of transactions.
+
+In versions earlier than 4.0, TiDB limits the total number of key-value pairs for a single transaction to no more than 300,000. This limitation is removed since v4.0.