Mysql Blob Partial Update
赵明寰 https://whoiami.github.io/
Long Story Short
Blob 在做partial update 并且符合small change 记录到undo record ，之后如果读请求走mvcc 读到这个undo record 的时候有概率造成crash。
场景复现
环境8.0.25
client1
create table t (a int primary key, b json);
insert into t values (1, '[ "abc", "def" ]');
update t set b=JSON_SET(b, '$[0]', REPEAT('w', 10000));
client2
set SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ;
begin;
select * from t where a =1;
client1
UPDATE t SET b = JSON_REMOVE(b, '$[1]') where a = 1;
client2
select * from t where a =1;
