DSL, and SQL query very slow - sql

Question

This question is both about Doctrine and Symfony2.
I've made a query using Doctrine DQL. And Doctrine generates an SQL like this;
SELECT f0_.id AS id0, f0_.nom AS nom1, f0_.prenom AS prenom2, f0_.email AS email3, p1_.move_distance AS move_distance4, a2_.adresse1 AS adresse15, a2_.adresse2 AS adresse26, p3_.nom AS nom7, v4_.nom AS nom8, v4_.url AS url9, v4_.cp AS cp10, v4_.insee AS insee11, v4_.lat AS lat12, v4_.lng AS lng13, COUNT(f0_.id) AS sclr17
FROM person_teacher p1_
INNER JOIN fos_user f0_ ON p1_.id = f0_.id
LEFT JOIN person_lesson p7_ ON f0_.id = p7_.person_id
LEFT JOIN lesson l6_ ON l6_.id = p7_.lesson_id AND (l6_.id = 1)
LEFT JOIN person_teacher_language p9_ ON p1_.id = p9_.personteacher_id
LEFT JOIN language l8_ ON l8_.id = p9_.language_id AND (l8_.id = 1)
LEFT JOIN note_value n10_ ON p1_.id = n10_.personTeacher_id
LEFT JOIN pays p3_ ON f0_.id_pays = p3_.id
LEFT JOIN note n5_ ON n10_.id_note = n5_.id
LEFT JOIN person_teacher_adresse p11_ ON p1_.id = p11_.personteacher_id
LEFT JOIN adresse a2_ ON a2_.id = p11_.adresse_id
LEFT JOIN ville v4_ ON a2_.id_ville = v4_.id
GROUP BY f0_.id LIMIT 2147483647 OFFSET 0;
The problem is about these joins:
LEFT JOIN person_lesson p7_ ON f0_.id = p7_.person_id
LEFT JOIN lesson l6_ ON l6_.id = p7_.lesson_id AND (l6_.id = 1)
LEFT JOIN person_teacher_language p9_ ON p1_.id = p9_.personteacher_id
LEFT JOIN language l8_ ON l8_.id = p9_.language_id AND (l8_.id = 1)
If I remove them, the request works. Long request, but works.
With the joins, the request is infinite (99.9% CPU time used by MySQL after 5mn) or maybe very long, but anyway, far too long.
How to optimize this query?
(PS : I thought the AND (l6_.id = 1) and the AND (l8_.id = 1) would act as "filters" and immediately remove unnecessary rows, but no, it makes things worse: it's faster if I remove those conditions, and add where clause at the end, something like: WHERE (l6_.id = 1) AND (l8_.id = 1))
Here's my DQL code:
$retour = $this->createQueryBuilder('p')
->select(array(
'p.id',
'p.nom',
'p.prenom',
'p.email',
'p.moveDistance',
'a.adresse1',
'a.adresse2',
'pn.nom as pays',
'v.nom AS ville_nom',
'v.url',
'v.cp',
'v.insee',
'v.lat',
'v.lng',
'ROUND(' .
$mul.' * ' .
'ACOS( ' .
'COS( RADIANS( '.$lat.')) * '.
'COS( RADIANS( v.lat )) * '.
'COS( RADIANS( v.lng )-radians('.$lng.')) + '.
'SIN( RADIANS( '.$lat.' )) * '.
'SIN( RADIANS( v.lat )) ' .
')'.
',2) AS distance',
($in_kilometers?'\'km\'':'\'miles\'').' AS unit',
'ROUND( AVG(n.importance), 1) AS importance',
'COUNT(p.id) AS total'
))
->leftJoin('p.noteValues', 'nv')
->leftJoin('p.paysNaissance', 'pn')
->leftJoin('nv.note', 'n')
->leftJoin('p.adresses', 'a')
->leftJoin('a.ville', 'v');
/* (!) Optimizer: find out why if I do a join "ON"
* it endlessly query. I did classical "join" then a "WHERE"
* at the end. Find out why this method is faster:
*/
if ($lesson_id>0) {
$retour = $retour
->leftJoin('p.lessons', 'le');
}
if ($language_id>0) {
$retour = $retour
->leftJoin('p.languages', 'ln');
}
if (($lesson_id>0) && ($language_id>0)) {
$retour = $retour
->where('le.id = :lesson_id')
->andWhere('ln.id = :language_id');
}
elseif ($lesson_id>0) {
$retour = $retour
->where('le.id = :lesson_id');
}
elseif ($language_id>0) {
$retour = $retour
->where('ln.id = :language_id');
}
$retour = $retour
->groupBy('p.id')
->having('distance>:dmin')
->andHaving('distance<=:dmax')
->addOrderBy($order_by_1, $order_sens_1)
->addOrderBy($order_by_2, $order_sens_2);
$params=array(
'dmin' => $distance_min,
'dmax' => $distance_max
);
if ($lesson_id>0) {
$params['lesson_id']= $lesson_id;
}
if ($language_id>0) {
$params['language_id']= $language_id;
}
$retour = $retour->setParameters($params);
$retour = $retour
->setFirstResult( $offset )
->setMaxResults( $limit );
return $retour;

Answer 1

I suggest to put the table with more rows after the FROM part of the select,
and change the line 'LEFT JOIN lesson l6_ ON l6_.id = p7_.lesson_id AND (l6_.id = 1)' this way : It seems that you don't need to join with p7 because you force to be l6_.id=1, so I change to this
'LEFT JOIN lesson l6_ ON (l6_.id = 1)'
Hope this help.

Answer 2

Without a look at your MySQL table definitions, to speed up your query make sure you have defined an index on each column involved in a join, because otherwise mysql must evaluate each record of the tables that miss the index.
Please add more details to your question and I'll edit the answer to reflect the changes.