SQL query takes very long - mysql

Question

I have a table, named Ads, which contains ~441.000 rows, and 21 columns.
I am trying to run the following query:
SELECT Ads.* FROM Ads WHERE Ads.countries_CountryId = 'FR'
I put an index, to the countries_CountryId field, which is of type char(2), but when I run the above query, it takes around 5-8 seconds to complete. This ammount of time looks immensly high for me, for such a medium sized table, and such a simple SQL query. Where should I look for the problem? Or is it normal for such a query to take so long?
I also tried to EXPLAIN the above query, and get the following results, but I don't know how to decipher this:(
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE Ads ref countries_CountryId countries_CountryId 2 const 24368 Using where
EDIT1: (response to Seth McClaine)
I've tried your suggestion, the way you suggested, returns an error, but if I run SELECT count(*) FROM Ads WHERE Ads.countries_CountryId = 'FR', it runs much much faster: 0.0052490234375
But the problem is, I am not printing out anything, I am using php to run the queries, and calculating their runtime for the moment, and at the end, outputting the queries run, and the time they took:
Array
(
[0] => Array
(
[query] => SET character_set_results = 'utf8', character_set_client = 'utf8', character_set_connection = 'utf8', character_set_database = 'utf8', character_set_server = 'utf8'
[duration] => 0.00481009483337
)
[1] => Array
(
[query] => SELECT * FROM Countries WHERE NameFormatted LIKE '%FRANCE%'
[duration] => 0.00234889984131
)
[2] => Array
(
[query] => SELECT Ads.* FROM Ads WHERE Ads.countries_CountryId = 'FR'
[duration] => 4.71820402145
)
[3] => Array
(
[query] => SELECT COUNT(*) FROM Ads WHERE Ads.countries_CountryId = 'FR'
[duration] => 0.0052490234375
)
)
Here's also the code snippet, that runs the queries:
public function query($query, $cacheit=true) {
if (!$this->isConnected()) {
$this->throwError("Querying <b>".$query."</b> failed, because MySQL is not connected!", self::MYSQL_NOT_CONNECTED, false);
return false;
}
$qstart=microtime(true);
$result=#mysql_query($query, $this->conn_resource);
$qduration=microtime(true) - $qstart;
if ($result===FALSE) $this->throwError("Querying <b>".$query."</b> failed!", self::MYSQL_QUERY_ERR);
$this->numQueries++;
$this->executedQueries[] = array(
'query' => $query,
'duration' => $qduration
);
return $result;
}

Answer 1

Have your tried executing the query in read-only mode?
As explained here in mysql documentation.
You may try starting your query with
START TRANSACTION READ ONLY
Also, you may want to try using explain statement to get more information about your query.
EXPLAIN SELECT Ads.* FROM ....
Hope this helps. Helped for me in several large queries.