MySQL Bugs: #100698: Awfully vague statement regarding doubling slashes in REGEXP arguments

Bug #100698	Awfully vague statement regarding doubling slashes in REGEXP arguments
Submitted:	31 Aug 2020 15:03	Modified:	11 Feb 2021 15:02
Reporter:	teo teo	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Documentation	Severity:	S2 (Serious)
Version:	8.0	OS:	Any
Assigned to:		CPU Architecture:	Any

Description:
https://dev.mysql.com/doc/refman/8.0/en/regexp.html#operator_regexp

This statement is outrageously vague:

"Note
Because MySQL uses the C escape syntax in strings (for example, \n to represent the newline character), you must double any \ that you use in your expr and pat arguments.
"

Taken as-is, it's outright false. For example:

  SELECT * FROM sometable WHERE somefield REGEXP 'foo\n'

That is, if you want to match a \n newline character, you must NOT double the slash in the pattern.

So, what is "any \ that you use" supposed to mean? Whether or not you need to double a slash clearly depends on what the slash is used for, so more context is needed.

You need to either state that more rigorously, or add more examples, or both.

And that's only for the pattern operand. I guess it gets even more subtle for the other  operand.

How to repeat:
...

Thank you for the bug report.

Posted by developer:
 
The statement refers to inclusion of a literal \ character.

MySQL uses C escape syntax in strings (for example, \n to represent
the newline character). If you want your expr or pat argument to
contain a literal \, you must double it.

So why are you closing the report?