Retrieving Data & Results Sets

class Cake\ORM\Table

While table objects provide an abstraction around a ‘repository’ or collection of objects, when you query for individual records you get ‘entity’ objects. While this section discusses the different ways you can find and load entities, you should read the Entities section for more information on entities.

Debugging Queries and ResultSets

Since the ORM now returns Collections and Entities, debugging these objects can be more complicated than in previous CakePHP versions. There are now various ways to inspect the data returned by the ORM.

  • debug($query) Shows the SQL and bound params, does not show results.
  • debug($query->all()) Shows the ResultSet properties (not the results).
  • debug($query->toArray()) An easy way to show each of the results.
  • debug(json_encode($query, JSON_PRETTY_PRINT)) More human readable results.
  • debug($query->first()) Show the properties of a single entity.
  • debug((string)$query->first()) Show the properties of a single entity as JSON.

Getting a Single Entity by Primary Key

Cake\ORM\Table::get($id, $options = [])

It is often convenient to load a single entity from the database when editing or view entities and their related data. You can do this by using get():

// In a controller or table method.

// Get a single article
$article = $articles->get($id);

// Get a single article, and related comments
$article = $articles->get($id, [
    'contain' => ['Comments']
]);

If the get operation does not find any results a Cake\Datasource\Exception\RecordNotFoundException will be raised. You can either catch this exception yourself, or allow CakePHP to convert it into a 404 error.

Like find(), get() also has caching integrated. You can use the cache option when calling get() to perform read-through caching:

// In a controller or table method.

// Use any cache config or CacheEngine instance & a generated key
$article = $articles->get($id, [
    'cache' => 'custom',
]);

// Use any cache config or CacheEngine instance & specific key
$article = $articles->get($id, [
    'cache' => 'custom', 'key' => 'mykey'
]);

// Explicitly disable caching
$article = $articles->get($id, [
    'cache' => false
]);

Optionally you can get() an entity using Custom Finder Methods. For example you may want to get all translations for an entity. You can achieve that by using the finder option:

$article = $articles->get($id, [
    'finder' => 'translations',
]);

Using Finders to Load Data

Cake\ORM\Table::find($type, $options = [])

Before you can work with entities, you’ll need to load them. The easiest way to do this is using the find() method. The find method provides an easy and extensible way to find the data you are interested in:

// In a controller or table method.

// Find all the articles
$query = $articles->find('all');

The return value of any find() method is always a Cake\ORM\Query object. The Query class allows you to further refine a query after creating it. Query objects are evaluated lazily, and do not execute until you start fetching rows, convert it to an array, or when the all() method is called:

// In a controller or table method.

// Find all the articles.
// At this point the query has not run.
$query = $articles->find('all');

// Iteration will execute the query.
foreach ($query as $row) {
}

// Calling all() will execute the query
// and return the result set.
$results = $query->all();

// Once we have a result set we can get all the rows
$data = $results->toArray();

// Converting the query to an array will execute it.
$data = $query->toArray();

Note

Once you’ve started a query you can use the Query Builder interface to build more complex queries, adding additional conditions, limits, or include associations using the fluent interface.

// In a controller or table method.
$query = $articles->find('all')
    ->where(['Articles.created >' => new DateTime('-10 days')])
    ->contain(['Comments', 'Authors'])
    ->limit(10);

You can also provide many commonly used options to find(). This can help with testing as there are fewer methods to mock:

// In a controller or table method.
$query = $articles->find('all', [
    'conditions' => ['Articles.created >' => new DateTime('-10 days')],
    'contain' => ['Authors', 'Comments'],
    'limit' => 10
]);

The list of options supported by find() are:

  • conditions provide conditions for the WHERE clause of your query.
  • limit Set the number of rows you want.
  • offset Set the page offset you want. You can also use page to make the calculation simpler.
  • contain define the associations to eager load.
  • fields limit the fields loaded into the entity. Only loading some fields can cause entities to behave incorrectly.
  • group add a GROUP BY clause to your query. This is useful when using aggregating functions.
  • having add a HAVING clause to your query.
  • join define additional custom joins.
  • order order the result set.

Any options that are not in this list will be passed to beforeFind listeners where they can be used to modify the query object. You can use the getOptions() method on a query object to retrieve the options used. While you can pass query objects to your controllers, we recommend that you package your queries up as Custom Finder Methods instead. Using custom finder methods will let you re-use your queries and make testing easier.

By default queries and result sets will return Entities objects. You can retrieve basic arrays by disabling hydration:

$query->hydrate(false);

// $data is ResultSet that contains array data.
$data = $query->all();

Getting the First Result

The first() method allows you to fetch only the first row from a query. If the query has not been executed, a LIMIT 1 clause will be applied:

// In a controller or table method.
$query = $articles->find('all', [
    'order' => ['Articles.created' => 'DESC']
]);
$row = $query->first();

This approach replaces find('first') in previous versions of CakePHP. You may also want to use the get() method if you are loading entities by primary key.

Note

The first() method will return null if no results are found.

Getting a Count of Results

Once you have created a query object, you can use the count() method to get a result count of that query:

// In a controller or table method.
$query = $articles->find('all', [
    'conditions' => ['Articles.title LIKE' => '%Ovens%']
]);
$number = $query->count();

See Returning the Total Count of Records for additional usage of the count() method.

Finding Key/Value Pairs

It is often useful to generate an associative array of data from your application’s data. For example, this is very useful when creating <select> elements. CakePHP provides a simple to use method for generating ‘lists’ of data:

// In a controller or table method.
$query = $articles->find('list');
$data = $query->toArray();

// Data now looks like
$data = [
    1 => 'First post',
    2 => 'Second article I wrote',
];

With no additional options the keys of $data will be the primary key of your table, while the values will be the ‘displayField’ of the table. You can use the displayField() method on a table object to configure the display field of a table:

class ArticlesTable extends Table
{

    public function initialize(array $config)
    {
        $this->displayField('title');
    }
}

When calling list you can configure the fields used for the key and value with the keyField and valueField options respectively:

// In a controller or table method.
$query = $articles->find('list', [
    'keyField' => 'slug',
    'valueField' => 'title'
]);
$data = $query->toArray();

// Data now looks like
$data = [
    'first-post' => 'First post',
    'second-article-i-wrote' => 'Second article I wrote',
];

Results can be grouped into nested sets. This is useful when you want bucketed sets, or want to build <optgroup> elements with FormHelper:

// In a controller or table method.
$query = $articles->find('list', [
    'keyField' => 'slug',
    'valueField' => 'title',
    'groupField' => 'author_id'
]);
$data = $query->toArray();

// Data now looks like
$data = [
    1 => [
        'first-post' => 'First post',
        'second-article-i-wrote' => 'Second article I wrote',
    ],
    2 => [
        // More data.
    ]
];

You can also create list data from associations that can be reached with joins:

$query = $articles->find('list', [
    'keyField' => 'id',
    'valueField' => 'author.name'
])->contain(['Authors']);

Customize Key-Value Output

Lastly it is possible to use closures to access entity accessor methods in your list finds.

// In your Authors Entity create a virtual field to be used as the displayField:
protected function _getLabel()
{
    return $this->_properties['first_name'] . ' ' . $this->_properties['last_name']
      . ' / ' . __('User ID %s', $this->_properties['user_id']);
}

This example shows using the _getLabel() accessor method from the Author entity.

// In your finders/controller:
$query = $articles->find('list', [
    'keyField' => 'id',
    'valueField' => function ($article) {
        return $article->author->get('label');
    }
]);

You can also fetch the label in the list directly using.

// In AuthorsTable::initialize():
$this->displayField('label'); // Will utilize Author::_getLabel()
// In your finders/controller:
$query = $authors->find('list'); // Will utilize AuthorsTable::displayField()

Finding Threaded Data

The find('threaded') finder returns nested entities that are threaded together through a key field. By default this field is parent_id. This finder allows you to access data stored in an ‘adjacency list’ style table. All entities matching a given parent_id are placed under the children attribute:

// In a controller or table method.
$query = $comments->find('threaded');

// Expanded default values
$query = $comments->find('threaded', [
    'keyField' => $comments->primaryKey(),
    'parentField' => 'parent_id'
]);
$results = $query->toArray();

echo count($results[0]->children);
echo $results[0]->children[0]->comment;

The parentField and keyField keys can be used to define the fields that threading will occur on.

Tip

If you need to manage more advanced trees of data, consider using Tree instead.

Custom Finder Methods

The examples above show how to use the built-in all and list finders. However, it is possible and recommended that you implement your own finder methods. Finder methods are the ideal way to package up commonly used queries, allowing you to abstract query details into a simple to use method. Finder methods are defined by creating methods following the convention of findFoo where Foo is the name of the finder you want to create. For example if we wanted to add a finder to our articles table for finding published articles we would do the following:

use Cake\ORM\Query;
use Cake\ORM\Table;

class ArticlesTable extends Table
{

    public function findOwnedBy(Query $query, array $options)
    {
        $user = $options['user'];
        return $query->where(['author_id' => $user->id]);
    }

}

// In a controller or table method.
$articles = TableRegistry::get('Articles');
$query = $articles->find('ownedBy', ['user' => $userEntity]);

Finder methods can modify the query as required, or use the $options to customize the finder operation with relevant application logic. You can also ‘stack’ finders, allowing you to express complex queries effortlessly. Assuming you have both the ‘published’ and ‘recent’ finders, you could do the following:

// In a controller or table method.
$articles = TableRegistry::get('Articles');
$query = $articles->find('published')->find('recent');

While all the examples so far have show finder methods on table classes, finder methods can also be defined on Behaviors.

If you need to modify the results after they have been fetched you should use a Modifying Results with Map/Reduce function to modify the results. The map reduce features replace the ‘afterFind’ callback found in previous versions of CakePHP.

Dynamic Finders

CakePHP’s ORM provides dynamically constructed finder methods which allow you to express simple queries with no additional code. For example if you wanted to find a user by username you could do:

// In a controller
// The following two calls are equal.
$query = $this->Users->findByUsername('joebob');
$query = $this->Users->findAllByUsername('joebob');

// In a table method
$users = TableRegistry::get('Users');
// The following two calls are equal.
$query = $users->findByUsername('joebob');
$query = $users->findAllByUsername('joebob');

When using dynamic finders you can constrain on multiple fields:

$query = $users->findAllByUsernameAndApproved('joebob', 1);

You can also create OR conditions:

$query = $users->findAllByUsernameOrEmail('joebob', 'joe@example.com');

While you can use either OR or AND conditions, you cannot combine the two in a single dynamic finder. Other query options like contain are also not supported with dynamic finders. You should use Custom Finder Methods to encapsulate more complex queries. Lastly, you can also combine dynamic finders with custom finders:

$query = $users->findTrollsByUsername('bro');

The above would translate into the following:

$users->find('trolls', [
    'conditions' => ['username' => 'bro']
]);

Once you have a query object from a dynamic finder, you’ll need to call first() if you want the first result.

Note

While dynamic finders make it simple to express queries, they come with some additional performance overhead.

Retrieving Associated Data

When you want to grab associated data, or filter based on associated data, there are two ways:

  • use CakePHP ORM query functions like contain() and matching()
  • use join functions like innerJoin(), leftJoin(), and rightJoin()

You should use contain() when you want to load the primary model, and its associated data. While contain() will let you apply additional conditions to the loaded associations, you cannot constrain the primary model based on the associations. For more details on the contain(), look at Eager Loading Associations Via Contain.

You should use matching() when you want to restrict the primary model based on associations. For example, you want to load all the articles that have a specific tag on them. For more details on the matching(), look at Filtering by Associated Data Via Matching And Joins.

If you prefer to use join functions, you can look at Adding Joins for more information.

Eager Loading Associations Via Contain

By default CakePHP does not load any associated data when using find(). You need to ‘contain’ or eager-load each association you want loaded in your results.

Eager loading helps avoid many of the potential performance problems surrounding lazy-loading in an ORM. The queries generated by eager loading can better leverage joins, allowing more efficient queries to be made. In CakePHP you define eager loaded associations using the ‘contain’ method:

// In a controller or table method.

// As an option to find()
$query = $articles->find('all', ['contain' => ['Authors', 'Comments']]);

// As a method on the query object
$query = $articles->find('all');
$query->contain(['Authors', 'Comments']);

The above will load the related author and comments for each article in the result set. You can load nested associations using nested arrays to define the associations to be loaded:

$query = $articles->find()->contain([
    'Authors' => ['Addresses'], 'Comments' => ['Authors']
]);

Alternatively, you can express nested associations using the dot notation:

$query = $articles->find()->contain([
    'Authors.Addresses',
    'Comments.Authors'
]);

You can eager load associations as deep as you like:

$query = $products->find()->contain([
    'Shops.Cities.Countries',
    'Shops.Managers'
]);

You can select fields from all associations with multiple easy contain() statements:

$query = $this->find()->select([
    'Realestates.id',
    'Realestates.title',
    'Realestates.description'
])
->contain([
    'RealestateAttributes' => [
        'Attributes' => [
            'fields' => [
                // Aliased fields in contain() must include
                // the model prefix to be mapped correctly.
                'Attributes__name' => 'attr_name'
            ]
        ]
    ]
])
->contain([
    'RealestateAttributes' => [
        'fields' => [
            'RealestateAttributes.realestate_id',
            'RealestateAttributes.value'
        ]
    ]
])
->where($condition);

If you need to reset the containments on a query you can set the second argument to true:

$query = $articles->find();
$query->contain(['Authors', 'Comments'], true);

Passing Conditions to Contain

When using contain() you are able to restrict the data returned by the associations and filter them by conditions:

// In a controller or table method.

$query = $articles->find()->contain([
    'Comments' => function ($q) {
       return $q
            ->select(['body', 'author_id'])
            ->where(['Comments.approved' => true]);
    }
]);

This also works for pagination at the Controller level:

$this->paginate['contain'] = [
    'Comments' => function (\Cake\ORM\Query $query) {
        return $query->select(['body', 'author_id'])
        ->where(['Comments.approved' => true]);
    }
];

Note

When you limit the fields that are fetched from an association, you must ensure that the foreign key columns are selected. Failing to select foreign key fields will cause associated data to not be present in the final result.

It is also possible to restrict deeply-nested associations using the dot notation:

$query = $articles->find()->contain([
    'Comments',
    'Authors.Profiles' => function ($q) {
        return $q->where(['Profiles.is_published' => true]);
    }
]);

If you have defined some custom finder methods in your associated table, you can use them inside contain():

// Bring all articles, but only bring the comments that are approved and
// popular.
$query = $articles->find()->contain([
    'Comments' => function ($q) {
       return $q->find('approved')->find('popular');
    }
]);

Note

For BelongsTo and HasOne associations only the where and select clauses are used when loading the associated records. For the rest of the association types you can use every clause that the query object provides.

If you need full control over the query that is generated, you can tell contain() to not append the foreignKey constraints to the generated query. In that case you should use an array passing foreignKey and queryBuilder:

$query = $articles->find()->contain([
    'Authors' => [
        'foreignKey' => false,
        'queryBuilder' => function ($q) {
            return $q->where(...); // Full conditions for filtering
        }
    ]
]);

If you have limited the fields you are loading with select() but also want to load fields off of contained associations, you can pass the association object to select():

// Select id & title from articles, but all fields off of Users.
$query = $articles->find()
    ->select(['id', 'title'])
    ->select($articles->Users)
    ->contain(['Users']);

Alternatively, if you have multiple associations, you can use autoFields():

// Select id & title from articles, but all fields off of Users, Comments
// and Tags.
$query->select(['id', 'title'])
    ->contain(['Comments', 'Tags'])
    ->autoFields(true)
    ->contain(['Users' => function($q) {
        return $q->autoFields(true);
    }]);

New in version 3.1: Selecting columns via an association object was added in 3.1

Sorting Contained Associations

When loading HasMany and BelongsToMany associations, you can use the sort option to sort the data in those associations:

$query->contain([
    'Comments' => [
        'sort' => ['Comments.created' => 'DESC']
    ]
]);

Filtering by Associated Data Via Matching And Joins

A fairly common query case with associations is finding records ‘matching’ specific associated data. For example if you have ‘Articles belongsToMany Tags’ you will probably want to find Articles that have the CakePHP tag. This is extremely simple to do with the ORM in CakePHP:

// In a controller or table method.

$query = $articles->find();
$query->matching('Tags', function ($q) {
    return $q->where(['Tags.name' => 'CakePHP']);
});

You can apply this strategy to HasMany associations as well. For example if ‘Authors HasMany Articles’, you could find all the authors with recently published articles using the following:

$query = $authors->find();
$query->matching('Articles', function ($q) {
    return $q->where(['Articles.created >=' => new DateTime('-10 days')]);
});

Filtering by deep associations is surprisingly easy, and the syntax should be already familiar to you:

// In a controller or table method.
$query = $products->find()->matching(
    'Shops.Cities.Countries', function ($q) {
        return $q->where(['Countries.name' => 'Japan']);
    }
);

// Bring unique articles that were commented by 'markstory' using passed variable
// Dotted matching paths should be used over nested matching() calls
$username = 'markstory';
$query = $articles->find()->matching('Comments.Users', function ($q) use ($username) {
    return $q->where(['username' => $username]);
});

Note

As this function will create an INNER JOIN, you might want to consider calling distinct on the find query as you might get duplicate rows if your conditions don’t exclude them already. This might be the case, for example, when the same users comments more than once on a single article.

The data from the association that is ‘matched’ will be available on the _matchingData property of entities. If you both match and contain the same association, you can expect to get both the _matchingData and standard association properties in your results.

Using innerJoinWith

Using the matching() function, as we saw already, will create an INNER JOIN with the specified association and will also load the fields into the result set.

There may be cases where you want to use matching() but are not interested in loading the fields into the result set. For this purpose, you can use innerJoinWith():

$query = $articles->find();
$query->innerJoinWith('Tags', function ($q) {
    return $q->where(['Tags.name' => 'CakePHP']);
});

The innerJoinWith() method works the same as matching(), that means that you can use dot notation to join deeply nested associations:

$query = $products->find()->innerJoinWith(
    'Shops.Cities.Countries', function ($q) {
        return $q->where(['Countries.name' => 'Japan']);
    }
);

Again, the only difference is that no additional columns will be added to the result set, and no _matchingData property will be set.

New in version 3.1: Query::innerJoinWith() was added in 3.1

Using notMatching

The opposite of matching() is notMatching(). This function will change the query so that it filters results that have no relation to the specified association:

// In a controller or table method.

$query = $articlesTable
    ->find()
    ->notMatching('Tags', function ($q) {
        return $q->where(['Tags.name' => 'boring']);
    });

The above example will find all articles that were not tagged with the word boring. You can apply this method to HasMany associations as well. You could, for example, find all the authors with no published articles in the last 10 days:

$query = $authorsTable
    ->find()
    ->notMatching('Articles', function ($q) {
        return $q->where(['Articles.created >=' => new \DateTime('-10 days')]);
    });

It is also possible to use this method for filtering out records not matching deep associations. For example, you could find articles that have not been commented on by a certain user:

$query = $articlesTable
    ->find()
    ->notMatching('Comments.Users', function ($q) {
        return $q->where(['username' => 'jose']);
    });

Since articles with no comments at all also satisfy the condition above, you may want to combine matching() and notMatching() in the same query. The following example will find articles having at least one comment, but not commented by a certain user:

$query = $articlesTable
    ->find()
    ->notMatching('Comments.Users', function ($q) {
        return $q->where(['username' => 'jose']);
    })
    ->matching('Comments');

Note

As notMatching() will create a LEFT JOIN, you might want to consider calling distinct on the find query as you can get duplicate rows otherwise.

Keep in mind that contrary to the matching() function, notMatching() will not add any data to the _matchingData property in the results.

New in version 3.1: Query::notMatching() was added in 3.1

Using leftJoinWith

On certain occasions you may want to calculate a result based on an association, without having to load all the records for it. For example, if you wanted to load the total number of comments an article has along with all the article data, you can use the leftJoinWith() function:

$query = $articlesTable->find();
$query->select(['total_comments' => $query->func()->count('Comments.id')])
    ->leftJoinWith('Comments')
    ->group(['Articles.id'])
    ->autoFields(true);

The results for the above query will contain the article data and the total_comments property for each of them.

leftJoinWith() can also be used with deeply nested associations. This is useful, for example, for bringing the count of articles tagged with a certain word, per author:

$query = $authorsTable
    ->find()
    ->select(['total_articles' => $query->func()->count('Articles.id')])
    ->leftJoinWith('Articles.Tags', function ($q) {
        return $q->where(['Tags.name' => 'awesome']);
    })
    ->group(['Authors.id'])
    ->autoFields(true);

This function will not load any columns from the specified associations into the result set.

New in version 3.1: Query::leftJoinWith() was added in 3.1

Changing Fetching Strategies

As you may know already, belongsTo and hasOne associations are loaded using a JOIN in the main finder query. While this improves query and fetching speed and allows for creating more expressive conditions when retrieving data, this may be a problem when you want to apply certain clauses to the finder query for the association, such as order() or limit().

For example, if you wanted to get the first comment of an article as an association:

$articles->hasOne('FirstComment', [
     'className' => 'Comments',
     'foreignKey' => 'article_id'
]);

In order to correctly fetch the data from this association, we will need to tell the query to use the select strategy, since we want order by a particular column:

$query = $articles->find()->contain([
    'FirstComment' => [
            'strategy' => 'select',
            'queryBuilder' => function ($q) {
                return $q->order(['FirstComment.created' =>'ASC'])->limit(1);
            }
    ]
]);

Dynamically changing the strategy in this way will only apply to a specific query. If you want to make the strategy change permanent you can do:

$articles->FirstComment->strategy('select');

Using the select strategy is also a great way of making associations with tables in another database, since it would not be possible to fetch records using joins.

Fetching With The Subquery Strategy

As your tables grow in size, fetching associations from them can become slower, especially if you are querying big batches at once. A good way of optimizing association loading for hasMany and belongsToMany associations is by using the subquery strategy:

$query = $articles->find()->contain([
    'Comments' => [
            'strategy' => 'subquery',
            'queryBuilder' => function ($q) {
                return $q->where(['Comments.approved' => true]);
            }
    ]
]);

The result will remain the same as with using the default strategy, but this can greatly improve the query and fetching time in some databases, in particular it will allow to fetch big chunks of data at the same time in databases that limit the amount of bound parameters per query, such as Microsoft SQL Server.

You can also make the strategy permanent for the association by doing:

$articles->Comments->strategy('subquery');

Lazy Loading Associations

While CakePHP makes it easy to eager load your associations, there may be cases where you need to lazy-load associations. You should refer to the Lazy Loading Associations and Loading Additional Associations sections for more information.

Working with Result Sets

Once a query is executed with all(), you will get an instance of Cake\ORM\ResultSet. This object offers powerful ways to manipulate the resulting data from your queries. Like Query objects, ResultSets are a Collection and you can use any collection method on ResultSet objects.

Result set objects will lazily load rows from the underlying prepared statement. By default results will be buffered in memory allowing you to iterate a result set multiple times, or cache and iterate the results. If you need work with a data set that does not fit into memory you can disable buffering on the query to stream results:

$query->bufferResults(false);

Turning buffering off has a few caveats:

  1. You will not be able to iterate a result set more than once.
  2. You will also not be able to iterate & cache the results.
  3. Buffering cannot be disabled for queries that eager load hasMany or belongsToMany associations, as these association types require eagerly loading all results so that dependent queries can be generated.

Warning

Streaming results will still allocate memory for the entire results when using PostgreSQL and SQL Server. This is due to limitations in PDO.

Result sets allow you to cache/serialize or JSON encode results for API results:

// In a controller or table method.
$results = $query->all();

// Serialized
$serialized = serialize($results);

// Json
$json = json_encode($results);

Both serializing and JSON encoding result sets work as you would expect. The serialized data can be unserialized into a working result set. Converting to JSON respects hidden & virtual field settings on all entity objects within a result set.

In addition to making serialization easy, result sets are a ‘Collection’ object and support the same methods that collection objects do. For example, you can extract a list of unique tags on a collection of articles by running:

// In a controller or table method.
$articles = TableRegistry::get('Articles');
$query = $articles->find()->contain(['Tags']);

$reducer = function ($output, $value) {
    if (!in_array($value, $output)) {
        $output[] = $value;
    }
    return $output;
};

$uniqueTags = $query->all()
    ->extract('tags.name')
    ->reduce($reducer, []);

Some other examples of the collection methods being used with result sets are:

// Filter the rows by a calculated property
$filtered = $results->filter(function ($row) {
    return $row->is_recent;
});

// Create an associative array from result properties
$articles = TableRegistry::get('Articles');
$results = $articles->find()->contain(['Authors'])->all();

$authorList = $results->combine('id', 'author.name');

The Collections chapter has more detail on what can be done with result sets using the collections features. The Adding Calculated Fields section show how you can add calculated fields, or replace the result set.

Getting the First & Last Record From a ResultSet

You can use the first() and last() methods to get the respective records from a result set:

$result = $articles->find('all')->all();

// Get the first and/or last result.
$row = $result->first();
$row = $result->last();

Getting an Arbitrary Index From a ResultSet

You can use skip() and first() to get an arbitrary record from a ResultSet:

$result = $articles->find('all')->all();

// Get the 5th record
$row = $result->skip(4)->first();

Checking if a Query or ResultSet is Empty

You can use the isEmpty() method on a Query or ResultSet object to see if it has any rows in it. Calling isEmpty() on a Query object will evaluate the query:

// Check a query.
$query->isEmpty();

// Check results
$results = $query->all();
$results->isEmpty();

Loading Additional Associations

Once you’ve created a result set, you may need to load additional associations. This is the perfect time to lazily eager load data. You can load additional associations using loadInto():

$articles = $this->Articles->find()->all();
$withMore = $this->Articles->loadInto($articles, ['Comments', 'Users']);

You can eager load additional data into a single entity, or a collection of entities.

Modifying Results with Map/Reduce

More often than not, find operations require post-processing the data that is found in the database. While entities’ getter methods can take care of most of the virtual property generation or special data formatting, sometimes you need to change the data structure in a more fundamental way.

For those cases, the Query object offers the mapReduce() method, which is a way of processing results once they are fetched from the database.

A common example of changing the data structure is grouping results together based on certain conditions. For this task we can use the mapReduce() function. We need two callable functions the $mapper and the $reducer. The $mapper callable receives the current result from the database as first argument, the iteration key as second argument and finally it receives an instance of the MapReduce routine it is running:

$mapper = function ($article, $key, $mapReduce) {
    $status = 'published';
    if ($article->isDraft() || $article->isInReview()) {
        $status = 'unpublished';
    }
    $mapReduce->emitIntermediate($article, $status);
};

In the above example $mapper is calculating the status of an article, either published or unpublished, then it calls emitIntermediate() on the MapReduce instance. This method stores the article in the list of articles labelled as either published or unpublished.

The next step in the map-reduce process is to consolidate the final results. For each status created in the mapper, the $reducer function will be called so you can do any extra processing. This function will receive the list of articles in a particular “bucket” as the first parameter, the name of the “bucket” it needs to process as the second parameter, and again, as in the mapper() function, the instance of the MapReduce routine as the third parameter. In our example, we did not have to do any extra processing, so we just emit() the final results:

$reducer = function ($articles, $status, $mapReduce) {
    $mapReduce->emit($articles, $status);
};

Finally, we can put these two functions together to do the grouping:

$articlesByStatus = $articles->find()
    ->where(['author_id' => 1])
    ->mapReduce($mapper, $reducer);

foreach ($articlesByStatus as $status => $articles) {
    echo sprintf("There are %d %s articles", count($articles), $status);
}

The above will ouput the following lines:

There are 4 published articles
There are 5 unpublished articles

Of course, this is a simplistic example that could actually be solved in another way without the help of a map-reduce process. Now, let’s take a look at another example in which the reducer function will be needed to do something more than just emitting the results.

Calculating the most commonly mentioned words, where the articles contain information about CakePHP, as usual we need a mapper function:

$mapper = function ($article, $key, $mapReduce) {
    if (stripos('cakephp', $article['body']) === false) {
        return;
    }

    $words = array_map('strtolower', explode(' ', $article['body']));
    foreach ($words as $word) {
        $mapReduce->emitIntermediate($article['id'], $word);
    }
};

It first checks for whether the “cakephp” word is in the article’s body, and then breaks the body into individual words. Each word will create its own bucket where each article id will be stored. Now let’s reduce our results to only extract the count:

$reducer = function ($occurrences, $word, $mapReduce) {
    $mapReduce->emit(count($occurrences), $word);
}

Finally, we put everything together:

$articlesByStatus = $articles->find()
    ->where(['published' => true])
    ->andWhere(['published_date >=' => new DateTime('2014-01-01')])
    ->hydrate(false)
    ->mapReduce($mapper, $reducer);

This could return a very large array if we don’t clean stop words, but it could look something like this:

[
    'cakephp' => 100,
    'awesome' => 39,
    'impressive' => 57,
    'outstanding' => 10,
    'mind-blowing' => 83
]

One last example and you will be a map-reduce expert. Imagine you have a friends table and you want to find “fake friends” in our database, or better said, people who do not follow each other. Let’s start with our mapper() function:

$mapper = function ($rel, $key, $mr) {
    $mr->emitIntermediate($rel['source_user_id'], $rel['target_user_id']);
    $mr->emitIntermediate($rel['target_user_id'], $rel['source_target_id']);
};

We just duplicated our data to have a list of users each other user follows. Now it’s time to reduce it. For each call to the reducer, it will receive a list of followers per user:

// $friends list will look like
// repeated numbers mean that the relationship existed in both directions
[2, 5, 100, 2, 4]

$reducer = function ($friendsList, $user, $mr) {
    $friends = array_count_values($friendsList);
    foreach ($friends as $friend => $count) {
        if ($count < 2) {
            $mr->emit($friend, $user);
        }
    }
}

And we supply our functions to a query:

$fakeFriends = $friends->find()
    ->hydrate(false)
    ->mapReduce($mapper, $reducer)
    ->toArray();

This would return an array similar to this:

[
    1 => [2, 4],
    3 => [6]
    ...
]

The resulting array means, for example, that user with id 1 follows users 2 and 4, but those do not follow 1 back.

Stacking Multiple Operations

Using mapReduce in a query will not execute it immediately. The operation will be registered to be run as soon as the first result is attempted to be fetched. This allows you to keep chaining additional methods and filters to the query even after adding a map-reduce routine:

$query = $articles->find()
    ->where(['published' => true])
    ->mapReduce($mapper, $reducer);

// At a later point in your app:
$query->where(['created >=' => new DateTime('1 day ago')]);

This is particularly useful for building custom finder methods as described in the Custom Finder Methods section:

public function findPublished(Query $query, array $options)
{
    return $query->where(['published' => true]);
}

public function findRecent(Query $query, array $options)
{
    return $query->where(['created >=' => new DateTime('1 day ago')]);
}

public function findCommonWords(Query $query, array $options)
{
    // Same as in the common words example in the previous section
    $mapper = ...;
    $reducer = ...;
    return $query->mapReduce($mapper, $reducer);
}

$commonWords = $articles
    ->find('commonWords')
    ->find('published')
    ->find('recent');

Moreover, it is also possible to stack more than one mapReduce operation for a single query. For example, if we wanted to have the most commonly used words for articles, but then filter it to only return words that were mentioned more than 20 times across all articles:

$mapper = function ($count, $word, $mr) {
    if ($count > 20) {
        $mr->emit($count, $word);
    }
};

$articles->find('commonWords')->mapReduce($mapper);

Removing All Stacked Map-reduce Operations

Under some circumstances you may want to modify a Query object so that no mapReduce operations are executed at all. This can be done by calling the method with both parameters as null and the third parameter (overwrite) as true:

$query->mapReduce(null, null, true);