Bug #114740 mysql lost decimal's precision for json data type.
Submitted: 23 Apr 8:29 Modified: 25 Apr 7:41
Reporter: biao li Email Updates:
Status: Duplicate Impact on me:
None 
Category:MySQL Server: JSON Severity:S4 (Feature request)
Version:8.0.36 OS:Any
Assigned to: CPU Architecture:Any
Tags: decimal, json

[23 Apr 8:29] biao li
Description:
mysqld may lose decimal's precision in json's datatype.

mysqld use rapidjson to parse string json, however, rapidjson may lose precision  when it try to parse a mysql decimal type with c++'s double.

mysql> create database w1;
Query OK, 1 row affected (0.01 sec)

mysql> use w1;
Database changed
mysql> create table t1(id int, name json);
Query OK, 0 rows affected (0.33 sec)

mysql> insert into t1 values(1,'{"a":-99999999999999999999999999999999999.999999999999999999999999999998}');
Query OK, 1 row affected (0.11 sec)

mysql> select * from t1;
+------+--------------+
| id   | name         |
+------+--------------+
|    1 | {"a": -1e35} |
+------+--------------+
1 row in set (0.00 sec)

How to repeat:
create database w1;
use w1;
create table t1(id int, name json);
insert into t1 values(1,'{"a":-99999999999999999999999999999999999.999999999999999999999999999998}');
select * from t1;

Suggested fix:
Should support all mysql's datatype in JSON.
[23 Apr 8:46] MySQL Verification Team
Hello biao li,

Thank you for the enhancement request!

regards,
Umesh
[25 Apr 7:41] Knut Anders Hatlen
This looks like the same issue that is described in bug#83954. Closing as duplicate.
Thanks.