ISSUES-5697 fix insert and select query with mysql style identifier

[zhang2014]

#5697
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Category:

• Bug Fix

[alexey-milovidov]

The symbol name is unclear.
The fact that we escape all special characters with backslash escept c looks strange. Is it really consistent with MySQL?

[zhang2014]

MySQL sys.quote_identifier only describes the content of backquotes. When I use it for special character escaping, it has some truncation problems, such as: SELECT sys.quote_identifier('\ b')=`, the following is directly The result of using the AS clause escaping in MySQL, but I'm not sure if this is correct (because I'm not sure if MySQL Client treats them as special characters):

:) SELECT 1 AS `\b`;
+----+
| \b |
+----+
|  1 |
+----+
1 row in set (0.00 sec)

:) SELECT 1 AS `\f`;
+----+
| \f |
+----+
|  1 |
+----+
1 row in set (0.00 sec)

:) SELECT 1 AS `\n`;
+----+
| \n |
+----+
|  1 |
+----+
1 row in set (0.00 sec)

:) SELECT 1 AS `\r`;
+----+
| \r |
+----+
|  1 |
+----+
1 row in set (0.00 sec)

:) SELECT 1 AS `\t`;
+----+
| \t |
+----+
|  1 |
+----+
1 row in set (0.00 sec)

:) SELECT 1 AS `\0`;
+----+
| \0 |
+----+
|  1 |
+----+
1 row in set (0.00 sec)

:) SELECT 1 AS `\\`;
+----+
| \\ |
+----+
|  1 |
+----+
1 row in set (0.00 sec)

[alexey-milovidov]

Maybe we need to support `quoted``identifiers` in MySQL style in ClickHouse parser?

[zhang2014]

Sure, but now ClickHouse uses backslash to escape backquote, and any changes could cause version-compatibility problems. Are we sure we want todo this?

[alexey-milovidov]

I forgot that we already do it:

:) SELECT 1 `a``b`

SELECT 1 AS `a\`b`                                                                                                                                                                                
                                                                                                                                                                                                  
┌─a`b─┐
│   1 │                                                                                                                                                                                           
└─────┘

[alexey-milovidov]

We still have to do something with this name...
because the escape_symbol applies only to c character and C-style escaping is applied to other characters
and it is counterintuitive.

[alexey-milovidov]

template <
    char quote_character, /// Will escape this character in addition to the list of special characters.
    bool escape_quote_with_quote /// Should we escape quote character with quote character ('hello''world') instead of backslash. Other special characters will be escaped with backslash as usual.
    >