Float precision is different from MySQL

Description

Bug Report

When insert into float column, the data precision is not consistent with mysql.

The mysql default float precision is 6 and tidb is 8.

1. What did you do?

create table t (t float);
insert into t values(0.12345678912345); 

2. What did you expect to see? In Mysql 5.7

mysql> select * from t;
+----------+
| t        |
+----------+
| 0.123457 |
+----------+

3. What did you see instead?

In TiDB v3.0.0

tidb> select * from t;
+------------+
| t          |
+------------+
| 0.12345679 |
+------------+

4. What version of TiDB are you using (tidb-server -V or run select tidb_version(); on TiDB)?

tidb> select tidb_version();
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tidb_version()                                                                                                                                                                                                                                                                                              |
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Release Version: v3.0.0
Git Commit Hash: 60965b006877ca7234adaced7890d7b029ed1306
Git Branch: HEAD
UTC Build Time: 2019-06-28 12:14:07
GoVersion: go version go1.12 linux/amd64
Race Enabled: false
TiKV Min Version: 2.1.0-alpha.1-ff3dd160846b7d1aed9079c389fc188f7f5ea13e
Check Table Before Drop: false |
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

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Score

300

Mentor

• @lzmhhh123