Incompatible with MySQL 8.0 about create table with default expression

[lonng]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do?
   If possible, provide a recipe for reproducing the error.

➜  ~ tidiff 'create table ttest ( a int(10) default (rand()))'
MySQL(127.0.0.1:3306)> create table ttest ( a int(10) default (rand()))
Query OK (0.007 sec)

TiDB(127.0.0.1:4000)> create table ttest ( a int(10) default (rand()))
Error 1105: line 1 column 40 near "rand()))" (total length 48)

➜  ~ tidiff 'desc ttest'
MySQL(127.0.0.1:3306)> desc ttest
+------------------------------------------------------------+
| Field | Type    | Null | Key | Default | Extra             |
+------------------------------------------------------------+
| a     | int(10) | YES  |     | rand()  | DEFAULT_GENERATED |
+------------------------------------------------------------+
1 row in set (0.003 sec)

TiDB(127.0.0.1:4000)> desc ttest
Error 1146: Table 'test.ttest' doesn't exist

2. What did you expect to see?

Create table successfully.

3. What did you see instead?

Error message show above.

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

TiDB(127.0.0.1:4000)> select tidb_version()
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tidb_version()                                                                                                                                                                                                                                                                                                                            |
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Release Version: v2.1.8-24-g7b36cdfb6-dirty
Git Commit Hash: 7b36cdfb6e8a4c279fc360ed79cf1c499b553688
Git Branch: failpoint-2.1
UTC Build Time: 2019-04-30 08:26:17
GoVersion: go version go1.12 darwin/amd64
Race Enabled: false
TiKV Min Version: 2.1.0-alpha.1-ff3dd160846b7d1aed9079c389fc188f7f5ea13e
Check Table Before Drop: false |
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.002 sec)

This is not a bug, but a MySQL 8.0 compatibility issue. Functions as default values was added after 8.0 GA. Here is the output from MySQL 5.7-latest:

mysql [localhost:5731] {msandbox} (test) > create table ttest ( a int(10) default (rand()));
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '(rand()))' at line 1

[morgo]

The matching parser issue is pingcap/parser#1347