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CREATE TABLE profile_category (
  id mediumint UNSIGNED NOT NULL AUTO_INCREMENT,
  pc_name char(255) NOT NULL,
  PRIMARY KEY (id),
  UNIQUE KEY idx_name (name)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

This is one of the tables in database that is entirely in utf8 charset. The problem is here (and I didn't new about it until now) that index for pc_name column will triple times bigger, because MySQL reserves 3 bites for every char. In this case indexes will take much more space.

I cannot make shorter index, because I need this value to be unique. One of the solutions could be set pc_name char(255) CHARSET latin1 NOT NULL, but I dont't know if this is a problem or not. Is this is a good Idea, or are there any solutions that I don't know ?

Update: the pc_name column is validated in application to be valid utf8. And it allows non western characters. But in this case I can just make a trade of and allow only /[_A-Za-z]/ if the case is worth it.

Update 2: I tried to set pc_name to latin1 charset, but now I get exceptions like: Zend_Db_Statement_Exception: SQLSTATE[HY000]: General error: 1267 Illegal mix of collations (latin1_swedish_ci,IMPLICIT) and (utf8_general_ci,COERCIBLE) for operation '='

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If pc_name is going to contain non-Western text then latin1 isn't going to be an option here - otherwise, go for it.

Not being a hardcore MySQL'er, I don't know if mixing InnoDB and MySQL tables is fraught with problems - if not, perhaps you could make this table a standard MySQL table and leave it as utf8?

于 2010-08-08T19:28:55.927 回答