I have the following relationships set up:
A HABTM B
B belongsTo C
C hasMany B
Now, for a given A, I need all C with the B's attached. I can write the SQL queries, but what's the proper CakePHP way? What method do I call on which model, and with which parameters?
I'd go with Aziz' answer and simply process the data as it comes in. If you need C to be your primary model though, you'll have to do a little workaround. Cake is not terrifically good with conditions on related models yet, especially on removed 3rd cousins kind of queries. It usually only does actual JOIN queries on belongsTo or hasMany relations; not on HABTM relations though, those it gets in separate queries. That means you can't include conditions on related HABTM models.
Your best bet then might be something like this:
// get related records as usual with the condition on A, limit to as little data as necessary
$ids = $this->A->find('first', array(
'conditions' => array('A.id' => 'something'),
'recursive' => 2,
'fields' => array('A.id'),
'contain' => array('B.id', 'B.c_id', 'B.C.id') // not quite sure if B.C.id works, maybe go with B.C instead
));
// find Cs, using the ids we got before as the condition
$Cs = $this->C->find('all', array(
'conditions' => array('C.id' => Set::extract('/B/C/id', $ids)),
'recursive => 1
);
Note that this produces quite a bunch of queries, so it's not really an optimal solution. Writing your own SQL might actually be the cleanest way.
EDIT:
Alternatively, you could re-bind your associations on the fly to make them hasMany/belongsTo relationships, most likely using the join table/model of A and B. That might enable you to use conditions on related models more easily, but it's still tricky to fetch Cs when the condition is on A.
$this->A->find(
'first',
array('conditions'=>array('id'=>'someword'),
'recursive'=>2)
);
like this?
this might work
$this->C->find('all',
array('conditions'=>array('id'=>'someword','B.aid'=>$a.id)));
I'd think of "Containable" behaviour (http://book.cakephp.org/view/474/Containable)... gives a lot control on finding related data.
Related
What I want to do is to get all rows related with user_id but in a different way.
First condition is to get all Books that are related with the User via Resources table where user_id is stored (in other words - Books owned by the User). Second condition is to get all Books that are related with the User through the Cities model again which is stored in the Resources table as well (Books that belong to Cities owned by the User).
I tried really a lot of things and I simply cannot make this two conditions work because I use JOIN (tried different combinations of innerJoinWith and leftJoinWith) on the same "end" model (User).
What I've done so far:
$userBooks = $this->Books->find()
->leftJoinWith("Resources.Users")
->leftJoinWith("Cities.Resources.Users")
->where(["Resources.Users" => 1])
->orWhere(["Cities.Resources.Users" => 1])
->all();
This of course does not work, but I hope you get the point about what I'm trying to achieve. The best what I was able to get with trying different approaches is the result of only one JOIN statement what is logical.
Basically, this can be separated into 2 parts which gives expected result (but I do not prefer it because I want it done with one query of course):
$userBooks = $this->Books->find()
->innerJoinWith("Resources.Users", function($q) {
return $q->where(["Users.id" => 1]);
})
->all();
$userBooks2 = $this->Books->find()
->innerJoinWith("Cities.Resources.Users", function($q) {
return $q->where(["Users.id" => 1]);
})
->all();
Also, before this I created an SQL script which works well and result is like expected:
SELECT books.id FROM books, cities, users_resources WHERE
(users_resources.resource_id = books.resource_id AND users_resources.user_id = 1)
OR
(users_resources.resource_id = cities.resource_id AND books.city_id = cities.id AND users_resources.user_id = 1)
This query works and I want to transfer it into ORM styled query in CakePHP to get both Books that are owned by the user and the ones that are connected with the User via Cities. I want somehow to separate these joins to individually filter data like I did in the SQL query.
EDIT
I've tried #ndm solution but the result is the same as where there is only 1 association (User) - I was still able to get data based on only one join statement (second one was ignored). Due to the fact I had to move on, I ended up with
$userBooks = $this->Books->find()
->innerJoinWith("Cities.Resources.Users")
->where(["Users.id" => $userId])
->union($this->Books->find()
->innerJoinWith("Resources.Users")
->where(["Users.id" => $userId])
)
->all();
which outputs correct result but not in very effective way (by union of 2 queries). I would really like to know the best way to approach this as this is a very common case (filtering by related model (user) that is associated with other models).
The ORM (specifically the eager loader) doesn't allow joining the same alias multiple times.
This can be worked around in various ways, the most simple one probaly being creating a separate association with a unique alias. For example in your ResourcesTable, create another association to Users with a different alias, say Users2, like:
$this->belongsToMany('Users2', [
'className' => 'Users'
]);
Then you can use that association in the second leftJoinWith(), and apply the conditions accordingly:
$this->Books
->find()
->leftJoinWith('Resources.Users')
->leftJoinWith('Cities.Resources.Users2')
->where(['Users.id' => 1])
->orWhere(['Users2.id' => 1])
->group('Books.id')
->all();
And don't forget to group your books to avoid duplicate results.
You could also create the joins manually using leftJoin() or join() instead, where you can define the aliases on your own (or don't use any at all) so that there are no conflicts, for more complex queries that can be a tedious task though.
You could also use your two separate queries as subqueries for conditions on Books, or even create a union query from them, which however might perform worse...
See also
Cookbook > Database Access & ORM > Query Builder > Adding Joins
CakePHP Issues > Improve association data fetching
I'm using Yii2's ActiveRecord implementation in (hopefully) exactly the way it should be used, according to the docs.
Problem
In a quite simple setup with simple relations betweens the tables, fetching 10 results is fast, 100 is slow. 1000 is impossible. The database is extremely small and indexed perfectly. The problem is definitly Yii2's way to request data, not the db itself.
I'm using a standard ActiveDataProvider like:
$provider = new ActiveDataProvider([
'query' => Post::find(),
'pagination' => false // to get all records
]);
What I suspect
Debugging with the Yii2 toolbar showed thousands of single SELECTs for a simple request that should just get 50 rows from table A with some simple "JOINs" to table B to table C. In plain SQL everybody would solve this with one SQL statement and two joins. Yii2 however fires a SELECT for every relation in every row (which makes sense to keep the ORM clean). Resulting in (more or less) 1 * 50 * 30 = 1500 queries for just getting two relations of each row.
Question
Why is Yii2 using so many single SELECTs, or is this a mistake on my side ?
Addionally, does anybody know how to "fix" this ?
As this is a very important issue for me I'll provide 500 bounty on May 14th.
By default, Yii2 uses lazy loading for better performance. The effect of this is that any relation is only fetched when you access it, hence the thousands of sql queries. You need to use eager loading. You can do this with \yii\db\ActiveQuery::with() which:
Specifies the relations with which this query should be performed
Say your relation is comments, the solution is as follows:
'query' => Post::find()->with('comments'),
From the guide for Relations, with will perform an extra query to get the relations i.e:
SELECT * FROM `post`;
SELECT * FROM `comment` WHERE `postid` IN (....);
To use proper joining, use joinWith with the eagerLoading parameter set to true instead:
This method allows you to reuse existing relation definitions to perform JOIN queries. Based on the definition of the specified relation(s), the method will append one or multiple JOIN statements to the current query.
So
'query' => Post::find()->joinWith('comments', true);
will result in the following queries:
SELECT `post`.* FROM `post` LEFT JOIN `comment` comments ON post.`id` = comments.`post_id`;
SELECT * FROM `comment` WHERE `postid` IN (....);
From #laslov's comment and https://github.com/yiisoft/yii2/issues/2379
it's important to realise that using joinWith() will not use the JOIN query to eagerly load the related data. For various reasons, even with the JOIN, the WHERE postid IN (...) query will still be executed to handle the eager loading. Thus, you should only use joinWith() when you specifically need a JOIN, e.g. to filter or order on one of the related table's columns
TLDR:
joinWith = with plus an actual JOIN (and therefore the ability to filter/order/group etc by one of the related columns)
In order to use relational AR, it is recommended that primary-foreign key constraints are declared for tables that need to be joined. The constraints will help to keep the consistency and integrity of the relational data.
Support for foreign key constraints varies in different DBMS. SQLite 3.6.19 or prior does not support foreign key constraints, but you can still declare the constraints when creating tables. MySQL’s MyISAM engine does not support foreign keys at all.
In AR, there are four types of relationships:
BELONGS_TO: if the relationship between table A and B is one-to-many, then B belongs to A (e.g. Post belongs to User);
HAS_MANY: if the relationship between table A and B is one-to-many, then A has many B (e.g. User has many Post);
HAS_ONE: this is special case of HAS_MANY where A has at most one B (e.g. User has at most one Profile);
MANY_MANY: this corresponds to the many-to-many relationship in database. An associative table is needed to break a many-to-many relationship into one-to-many relationships, as most DBMS do not support many-to-many relationship directly. In our example database schema, the tbl_post_category serves for this purpose. In AR terminology, we can explain MANY_MANY as the combination of BELONGS_TO and HAS_MANY. For example, Post belongs to many Category and Category has many Post.
The following code shows how we declare the relationships for the User and Post classes.
class Post extends CActiveRecord
{
......
public function relations()
{
return array(
'author'=>array(self::BELONGS_TO, 'User', 'author_id'),
'categories'=>array(self::MANY_MANY, 'Category',
'tbl_post_category(post_id, category_id)'),
);
}
}
class User extends CActiveRecord
{
......
public function relations()
{
return array(
'posts'=>array(self::HAS_MANY, 'Post', 'author_id'),
'profile'=>array(self::HAS_ONE, 'Profile', 'owner_id'),
);
}
}
The query result will be saved to the property as instance(s) of the related AR class. This is known as the lazy loading approach, i.e., the relational query is performed only when the related objects are initially accessed. The example below shows how to use this approach:
// retrieve the post whose ID is 10
$post=Post::model()->findByPk(10);
// retrieve the post's author: a relational query will be performed here
$author=$post->author;
You are somehow doing it the wrong please go through from the documentaion here http://www.yiiframework.com/doc/guide/1.1/en/database.arr
I know that it seems complicated, but I'll explain it.
I have 3 models, let's call them A, B and C.
All of them can be related to others via Many-to-Many relationships.
I want to check, if Model C is related with any Model B, which is related to my model.
I want to check it by "name" column of Model C instead of ID.
EDIT:
after some digging and asking around on irc it turned out that my previous approach was not at all a correct way to deal with this issue :)
Kudos to #Oddman and #Kindari for great input into the discussion - as suggested, to test whether two "many-to-many models" A and B are related you can use the lists method (Illuminate\Support\Collection)
in_array($b->id, $a->related()->lists('b_id'))
If next you want to check by 'name' if C is related to B, can you provide details on how is this column used in the relationship - do you have it present in the pivot table ? If so, maybe you can try the below - but it is only a wild guess of mine here...
in_array($c->name, $b->related()->lists('c_name'))
Apart from the above, you can always do a raw sql query with appropriate joins and it's a sure way to get it working. You can start off where #NDM suggests.
Surely a good thing to check out the docs as well:
http://four.laravel.com/docs/eloquent#many-to-many
http://four.laravel.com/docs/eloquent#working-with-pivot-tables
How about just using couple of inner joins? The good part with Eloquent is that you can always use Laravel's DB query builder as a part of the Eloquent model to handle more complicated cases as Eloquent is build upon Query builder.
$a = A::select('a.id, a.name, b.id, b.name, c.id, b.name')
->join('a_b_pivot', 'a.id', '=', 'b.a_id')
->join('b_c_pivot', 'b.id', '=', 'c.b_id')
->join('b', 'a_b_pivot.b_id', '=', 'b.id')
->join('c', 'b_c_pivot.c_id', '=', 'c.id')
->where('c.name', '=', $name);
Probably not the most efficient way but should work and should be more efficient than walking through the models and loading everything as models etc.
Just make sure you mention all fields with the table names or it doesn't work. Depending on what model you want back from the query, you could also start the query from C:: or B:: and tweak it according to that.
Other useful thing is probably using eager loading as a part of the query or ->load('b,c) after you get the results.
And don't forget you can create query scope out of this so it's easy to reuse anywhere in the code :)
I have a site developed in cakephp 2.0, I have some tables relationed here is an example:
This is my relations:
ingredients (id,name) has many versions
ingredient_properties(id,property_id,version_id) belongs
to properties, versions
properties (id,name,value,group_id,unit_id) has many
ingredient_properties and belongs to groups,units
groups (id,name) has many properties
units (id,name) has many properties
versions (id,name,ingredient_id,active) has many ingredient_properties and belongs to ingredients.
I am in the ingredientController.php and I wanto to retrieve all this data where Version.active=1 and Version.ingredient_id=2.
This is my query:
$this->set(
'ingredient',
$this->Ingredient->Version->find('all', array(
'recursive' => 2,
'conditions' => array(
'Version.active' => 1,
'Version.ingredient_id' => 2
)
))
);
I have many and many queries like this and I want to know if recursive 2 is the best way to retrieve all data of the table that I have explained or there is a better way most quickly (in terms of speed of query not to implement).
I hope that someone can help me to optimize my code because this query works but I don't know if it is the better way to retrieve data of many tables relationed.
Thanks.
It is not the best way to use 'recursive' => 2 if you want to retrieve so much data. I believe it generates too many queries. Containable behaviour has the same drawback. The best way for me was to unbind models associations and construct table joins on the fly. You can look at an example here. But you need to know some SQL to understand what you do.
I'm using cakephp. In some query I use these kind of find:
$this->Photo->Behaviors->attach('Containable', array('autoFields' => true));
This is the Contain array that i use in the find:
'contain'=>array(
'User'=>array('fields'=>array('User.Name','User.Username')),
'Like' => array('User'=>array('fields'=>'Name'),
'order'=>'Timestamp DESC'
)),
'recursive' => 2,
The problem is that every time i want the Name of User that liked a photo. Cakephp does this query.
For example: SELECT `User`.`Name` FROM `Users` AS `User` WHERE `User`.`id` = 2175
If i have 300 likes on one photo i will make another 300queries for the User.Name. So, I would like to cache this kind of request. I've installed memcache correctly in my server, it's working normally. But I can't find a way to cache the query that cake make with the Containable Behaviors.
Has some one had this problem?
Thanks
G.
Why not use cakephp's counterCache feature instead?
There is a lot of documentation in the cakephp book about caching queries not just in me cache but many other ways as well such. Check out the CakeCache class.
there are a number of approaches on this topic.
if it is only about belongsTo relations it boils down to manually join tables using bindModel().
here is a good behavior: http://planetcakephp.org/aggregator/items/891-linkable-behavior-taking-it-easy-in-your-db
it takes care of that itself.