Description:
In most utf8/utf8mb4 collations (other than utf8_turkish_ci and utf8_bin), I=i=İ, but ı is not treated as the same. That lowercase dotless I seems to be treated as a separate letter, between I and J.
For utf8_turkish_ci, this seems reasonable:
+------------+
| Equivalent |
+------------+
| I=ı |
| i=İ |
+------------+
For utf8_general_ci, this seems reasonable:
+------------+
| Equivalent |
+------------+
| I=i=İ=ı |
+------------+
For other collations, it seems 'wrong':
+------------+
| Equivalent |
+------------+
| I=i=İ |
| ı |
+------------+
For reference, here are the hex values:
+------+--------+
| c | hex(c) |
+------+--------+
| i | 69 |
| I | 49 |
| ı | C4B1 |
| İ | C4B0 |
+------+--------+
(I am not a linguist, but this seems wrong.)
How to repeat:
CREATE TABLE Dotless (
c CHAR(1) CHARACTER SET utf8
);
INSERT INTO Dotless (c) VALUES ('i'),('I'),('ı'),('İ');
SELECT GROUP_CONCAT(c ORDER BY HEX(c) SEPARATOR '=') AS Equivalent
FROM Dotless
GROUP BY c COLLATE utf8_turkish_ci;
SELECT GROUP_CONCAT(c ORDER BY HEX(c) SEPARATOR '=') AS Equivalent
FROM Dotless
GROUP BY c COLLATE utf8_general_ci;
SELECT GROUP_CONCAT(c ORDER BY HEX(c) SEPARATOR '=') AS Equivalent
FROM Dotless
GROUP BY c COLLATE utf8_unicode_ci;
SELECT GROUP_CONCAT(c ORDER BY HEX(c) SEPARATOR '=') AS Equivalent
FROM Dotless
GROUP BY c COLLATE utf8_unicode_520_ci;
# The `ORDER BY HEX(c)` is makes the 'equal' chars come out in a canonical order
Suggested fix:
I suspect this 'bug' (if it is such) should be nothing more than a footnote, especially after the fiasco with utf8_german_ci and the sharp-s.
I did not notice any other anomalies like this in the collations. (I doubt if 'ƒ' qualifies as an accented 'f'.)
This bug was prompted by this forum thread:
http://stackoverflow.com/questions/34462887/how-to-find-all-variations-accented-etc-of-a-s...
Description: In most utf8/utf8mb4 collations (other than utf8_turkish_ci and utf8_bin), I=i=İ, but ı is not treated as the same. That lowercase dotless I seems to be treated as a separate letter, between I and J. For utf8_turkish_ci, this seems reasonable: +------------+ | Equivalent | +------------+ | I=ı | | i=İ | +------------+ For utf8_general_ci, this seems reasonable: +------------+ | Equivalent | +------------+ | I=i=İ=ı | +------------+ For other collations, it seems 'wrong': +------------+ | Equivalent | +------------+ | I=i=İ | | ı | +------------+ For reference, here are the hex values: +------+--------+ | c | hex(c) | +------+--------+ | i | 69 | | I | 49 | | ı | C4B1 | | İ | C4B0 | +------+--------+ (I am not a linguist, but this seems wrong.) How to repeat: CREATE TABLE Dotless ( c CHAR(1) CHARACTER SET utf8 ); INSERT INTO Dotless (c) VALUES ('i'),('I'),('ı'),('İ'); SELECT GROUP_CONCAT(c ORDER BY HEX(c) SEPARATOR '=') AS Equivalent FROM Dotless GROUP BY c COLLATE utf8_turkish_ci; SELECT GROUP_CONCAT(c ORDER BY HEX(c) SEPARATOR '=') AS Equivalent FROM Dotless GROUP BY c COLLATE utf8_general_ci; SELECT GROUP_CONCAT(c ORDER BY HEX(c) SEPARATOR '=') AS Equivalent FROM Dotless GROUP BY c COLLATE utf8_unicode_ci; SELECT GROUP_CONCAT(c ORDER BY HEX(c) SEPARATOR '=') AS Equivalent FROM Dotless GROUP BY c COLLATE utf8_unicode_520_ci; # The `ORDER BY HEX(c)` is makes the 'equal' chars come out in a canonical order Suggested fix: I suspect this 'bug' (if it is such) should be nothing more than a footnote, especially after the fiasco with utf8_german_ci and the sharp-s. I did not notice any other anomalies like this in the collations. (I doubt if 'ƒ' qualifies as an accented 'f'.) This bug was prompted by this forum thread: http://stackoverflow.com/questions/34462887/how-to-find-all-variations-accented-etc-of-a-s...