Question

We have a simple search on our site that uses MySQL fulltext search and for some reason it doesn’t seem to be returning the correct results. I don’t know if it’s some kind of issue with Amazon RDS (where our database server resides) or with the query we are requesting.

Here is the structure of the database table:

CREATE TABLE `items` (
  `object_id` int(9) unsigned NOT NULL DEFAULT '0',
  `slug` varchar(100) DEFAULT NULL,
  `name` varchar(100) DEFAULT NULL,
  PRIMARY KEY (`object_id`),
  FULLTEXT KEY `name` (`name`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1;

And here is a simple fulltext search query on this table and the returned results:

select object_id ,slug,name from items where MATCH (name) AGAINST ('+ski*' IN BOOLEAN MODE) order by name;

+-----------+-----------------------------------+------------------+
| object_id | slug                              | name             |
+-----------+-----------------------------------+------------------+
|  10146041 | us/new-hampshire/dartmouth-skiway | Dartmouth Skiway |
+-----------+-----------------------------------+------------------+

If I instead use LIKE I get a different set of results:

select object_id,slug,name from items where name LIKE "%ski%" order by name;

+-----------+------------------------------------------+----------------------------------+
| object_id | slug                                     | name                             |
+-----------+------------------------------------------+----------------------------------+
|  10146546 | us/new-york/brantling-ski                | Brantling Ski                    |
|  10146548 | us/new-york/buffalo-ski-club             | Buffalo Ski Club                 |
|  10146041 | us/new-hampshire/dartmouth-skiway        | Dartmouth Skiway                 |
|  10146352 | us/montana/discover-ski                  | Discover Ski                     |
|  10144882 | us/california/donner-ski-ranch           | Donner Ski Ranch                 |
|  10146970 | us/new-york/hickory-ski-center           | Hickory Ski Center               |
|  10146973 | us/new-york/holimont-ski-area            | Holimont Ski Area                |
|  10146283 | us/minnesota/hyland-ski                  | Hyland Ski                       |
|  10145911 | us/nevada/las-vegas-ski-snowboard-resort | Las Vegas Ski & Snowboard Resort |
|  10146977 | us/new-york/maple-ski-ridge              | Maple Ski Ridge                  |
|  10146774 | us/oregon/mount-hood-ski-bowl            | Mt. Hood Ski Bowl                |
|  10145949 | us/new-mexico/sipapu-ski                 | Sipapu Ski                       |
|  10145952 | us/new-mexico/ski-apache                 | Ski Apache                       |
|  10146584 | us/north-carolina/ski-beech              | Ski Beech                        |
|  10147973 | canada/quebec/ski-bromont                | Ski Bromont                      |
|  10146106 | us/michigan/ski-brule                    | Ski Brule                        |
|  10145597 | us/massachusetts/ski-butternut           | Ski Butternut                    |
|  10145117 | us/colorado/ski-cooper                   | Ski Cooper                       |
|  10146917 | us/pennsylvania/ski-denton               | Ski Denton                       |
|  10145954 | us/new-mexico/ski-santa-fe               | Ski Santa Fe                     |
|  10146918 | us/pennsylvania/ski-sawmill              | Ski Sawmill                      |
|  10145299 | us/illinois/ski-snowstar                 | Ski Snowstar                     |
|  10145138 | us/connecticut/ski-sundown               | Ski Sundown                      |
|  10145598 | us/massachusetts/ski-ward                | Ski Ward                         |
+-----------+------------------------------------------+----------------------------------+

I’m at a complete loss as to why the query using fulltext search is not working. I’m hoping that some MySQL expert out there can point out the error in our query.

Thanks in advance for your help!

Answer 1

From MySQL docs

• + A leading plus sign indicates
  that this word must be present in
  each row that is returned.

• * The asterisk serves as the
  truncation (or wildcard) operator.
  Unlike the other operators, it should
  be appended to the word to be
  affected. Words match if they begin
  with the word preceding the *
  operator.

  If a word is specified with the
  truncation operator, it is not
  stripped from a boolean query, even
  if it is too short (as determined
  from the ft_min_word_len setting) or
  a stopword. This occurs because the
  word is not seen as too short or a
  stopword, but as a prefix that must
  be present in the document in the
  form of a word that begins with the
  prefix.

In Context:

MATCH(…) AGAINST(…)

MATCH (name) AGAINST ('+ski*' IN BOOLEAN MODE) means that you’re searching for rows where a word in the name column must contain ski, and must begin with the word ski.

From the set you’ve posted, Dartmouth Skiway is the only name that conforms to these requirements: it contains the word ski, and is prefixed by the word ski.

The other name columns, though they match the first rule: must contain ski, they are not prefixed with ski, as stipulated in your rule. The row returned by your boolean search is the only one with a name column that contains a word that both contains ski and is a word prefixed by ski.

As suggested by ajreal, try decreasing the ft_min_len_word_setting in my.cnf. Your search might be failing to come up with the results you expect because of the default setting. Try reducing it to 3.

WHERE column LIKE %text%

WHERE name LIKE "%ski%" searches for rows with name columns that contain ski, no matter where the word occurs.