MySQL Bugs: #96405: Syntax error with || when using PIPES_AS

Bug #96405	Syntax error with \|\| when using PIPES_AS_CONCAT after upgrading to 8.0.17
Submitted:	1 Aug 2019 20:04	Modified:	26 Aug 2019 16:14
Reporter:	Viktar Basharymau	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Parser	Severity:	S3 (Non-critical)
Version:	8.0.17	OS:	Any
Assigned to:		CPU Architecture:	Any
Tags:	parse error, PIPES_AS_CONCAT, regression

Description:
After upgrading from 8.0.16 to 8.0.17, some queries containing `||` stopped compiling even though PIPES_AS_CONCAT mode is set.

Here is an example:

```
SET sql_mode=(SELECT CONCAT(@@sql_mode, ',PIPES_AS_CONCAT'))
SELECT 'ab' LIKE 'a' || '%'
```

It works fine on 8.0.16, but fails with parse error on 8.0.17.

```
ERROR 1064 (42000) at line 1: 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 '|| '%'' at line 1
```

Note that adding brackets around `'a' || '%'` fixes the problem, but this is not an ideal solution because it requires software upgrade of the apps that use mysql, which can be costly and time-consuming.

Related issue: https://github.com/diesel-rs/diesel/issues/2133 

How to repeat:
Run the script below.

```
SET sql_mode=(SELECT CONCAT(@@sql_mode, ',PIPES_AS_CONCAT'))
SELECT 'ab' LIKE 'a' || '%'
```

Works in 8.0.16, broken in 8.0.17.

Hello Viktar,

Thank you for the report.

regards,
Umesh

Posted by developer:
 
Fixed in 8.0.18.

Some statements containing || produced a parse error even with the
PIPES_AS_CONCAT SQL mode enabled.