MySQL madness and Rails | Hacker News Reader

MySQL madness and Rails

phenoelit.org

13 pointsnperson5 comments

At the end of the post, the author says: "this issue wont be fixed for now." I asked on Twitter for more details, and this was his reply:

> response was roughly like "We might change this in Rails 4" and "$affected_lib should fix it on its side"[1]

[1] https://twitter.com/joernchen/status/298836052410519552

> For comparisons of a string column with a number, MySQL cannot use an index on the column to look up the value quickly. If str_col is an indexed string column, the index cannot be used when performing the lookup in the following statement:

> SELECT * FROM tbl_name WHERE str_col=1;

add index please

Am I missing something?

SELECT * FROM user WHERE "string" = 0;

will indeed match all users, but

SELECT * FROM user WHERE token = 0;

will not. (Presuming the token is stored in a table column)

Rails will do the following:

User.find_by_reset_password_token(0)

  User Load (0.8ms)  SELECT `users`.* FROM `users` WHERE `users`.`reset_password_token` = 0 LIMIT 1

 => #<User id: 1,[...]

hope that illustrates it

You're right, I was testing with tokens that started with numbers, so 0 didn't match anything.

  SELECT * FROM users where reset_token = 0;

will match the token "abc";

  SELECT * FROM users where reset_token = 1;

will match the token "1abc";

  SELECT * FROM users where reset_token = 123;

will match the token "123aasfas".

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