Double Encoding / Full Text Problems with MySQL 5.1

written on Sunday, September 26, 2010


This is an old blog post. I don't recommend to use mysql at all. Switch to PostgreSQL, as I did, it's so much better.

As I updated MySQL from 5.0 to 5.1 (due to Debian I'm not always as uptodate as others) I realized that I had huge problems with the fulltext indexes.

The following FTS example seemed not to work:

`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(80) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL,
FULLTEXT KEY `nameFull` (`name`)

insert into `fullTextTable` (name) values('bärtsch'),('börtsch'),('böll'),('büll');

select * from `fullTextTable` where match(name) against('+bärtsch' in boolean mode);

drop table `fullTextTable`;
| id | name |
| 1 | bärtsch |
| 2 | börtsch |
| 3 | böll |

With the help of the MySQL forums I realized that the cause was a double encoding. The length of böll for example was not 5, but 7.

Solving it was not a huge thing, just one query:

update test set fileNew = binary convert(file using latin1)

Since the MySQL convert command doesn't work the expected way, you have to use the binary command before the convert.

To check if everything worked out the way i wanted it, I used:

select * from test where file != convert(convert((binary fileNew) using latin1) using utf8);

The double encoding was just a little bug in my php interface: I did not use "set names utf8". Setting it after connecting has solved my problems.

If you plan on using fulltext indexes, I would seriously recommend checking your charsets.

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This entry was tagged mysql

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