MySQL fulltext search over multiple columns does not deliver the expected results

Question

I have a table called 'uploads'. The columns are id, date, last_update, description, tags. And I added the fulltext index 'description_tags' which includes those both columns description and tags. The table format is MyISAM. I am using USBWebserver if this could be the problem.

Now I try to select the uploads which have the provided GET variables in them.

MATCH (description,tags) AGAINST ("'.urldecode($_GET['tags']).'")

But the problems with the results I have are: There is no result when i search for 'lorem', but there is one when I add IN BOOLEAN MODE to the query. The 'Lorem' is actually in the description column. Searching keywords in the tags column don't have that problem. And even more interesting/annoying when I search for 'moree', which is also in the description table, I get results with and without the boolean mode...

What is the problem here? I don't see it.

Update

if ( $upload_display_sort == 'popular' )//sort by popularity

$query =    //select 'u' (a new defined variable?)
            'SELECT u.* '.
            //from the following table
            'FROM '.
            //uploads table as variable u
            'uploads u '.
            //join the following table
            'LEFT OUTER JOIN '.
            //select the column upload_id, count all columns into variable 'num' ???
            '(SELECT upload_id, COUNT(*) AS num '.
            //from the favorites table as variable f
            'FROM favorites f '.
            //and group it by the upload_id in the favorites table
            'GROUP BY upload_id) '.
            //what does this do? combine rows where the u.id == f.upload_id ???
            'f ON u.id = f.upload_id';

else $query = 'SELECT * FROM uploads';//select all from uploads



$query .=   ' WHERE online_state = 1';//select all online uploads



//FILTER FAVORITES

if  ($upload_display_sort == 'favorites' and !empty($favorites_ids))

$query .= ' AND id IN ('.implode(',', $favorites_ids).')';//returns 1,2,3,4,5

elseif  ($upload_display_sort == 'favorites' and empty($favorites_ids))

$query .= ' AND id IN (0)';//no upload id is 0



//FILTER SEARCH

if  (   isset($_GET['tags'])    )

$query .= ' AND MATCH (description,tags) AGAINST ("'.urldecode($_GET['tags']).'" IN BOOLEAN MODE)';



//FILTER DATE

if  (   isset($_GET['timeframe']    )

    and (   $_GET['timeframe'] == '3days'

        or  $_GET['timeframe'] == '2weeks'

        or  $_GET['timeframe'] == '3months')    )

{

    $end_date = time();//current time in unix format

    switch  (   $_GET['timeframe']  )

    {
        case '3days':   $start_date = strtotime('-3 days',$end_date);   break;
        case '2weeks':  $start_date = strtotime('-2 weeks',$end_date);  break;
        case '3months': $start_date = strtotime('-3 months',$end_date); break;
        default:        $start_date = strtotime('');    break;//1970-01-01 01:00:00
    }

    $end_date = date("Y-m-d H:i:s", $end_date);//current time in mysql format

    $start_date = date("Y-m-d H:i:s", $start_date);//end time in mysql format

    $query .= ' AND last_update BETWEEN "'.$start_date.'" AND "'.$end_date.'"';

}



//ORDER

$query .= ' ORDER BY';

if ( $upload_display_sort == 'popular' )//sort by popularity

$query .= ' f.num DESC,';

$query .= ' last_update DESC, id DESC';

Answer 1

Your test data may be incomplete. Note the following from the docs:

Words that are present in 50% or more of the rows are considered common and do not match.

Yet BOOLEAN MODE searches differ in that:

They do not use the 50% threshold.

I'm guessing "lorem" appears in 50% or more of the rows.

BOOLEAN MODE full text searches don't automatically sort by decreasing relevance. You'll need to sort them yourself like this:

SELECT *, MATCH (description,tags) AGAINST ("lorem") AS relevance
FROM uploads
WHERE MATCH (description,tags) AGAINST ("lorem" IN BOOLEAN MODE)
ORDER BY relevance DESC