MongoCollection::group
(PECL mongo >=0.9.2)
MongoCollection::group — Performs an operation similar to SQL's GROUP BY command
Описание
Список параметров
-
keys -
Fields to group by. If an array or non-code object is passed, it will be the key used to group results.
1.0.4+: If
keysis an instance of MongoCode,keyswill be treated as a function that returns the key to group by (see the "Passing akeysfunction" example below). -
initial -
Initial value of the aggregation counter object.
-
reduce -
A function that takes two arguments (the current document and the aggregation to this point) and does the aggregation.
-
options -
Optional parameters to the group command. Valid options include:
-
"condition"
Criteria for including a document in the aggregation.
-
"finalize"
Function called once per unique key that takes the final output of the reduce function.
"maxTimeMS"
Specifies a cumulative time limit in milliseconds for processing the operation (does not include idle time). If the operation is not completed within the timeout period, a MongoExecutionTimeoutException will be thrown.
-
Возвращаемые значения
Returns an array containing the result.
Список изменений
| Версия | Описание |
|---|---|
| 1.5.0 | Added "maxTimeMS" option. |
| 1.2.11 |
Emits E_DEPRECATED when
options is scalar.
|
Примеры
Пример #1 MongoCollection::group() example
This groups documents by category and creates a list of names within that category.
<?php
$collection->insert(array("category" => "fruit", "name" => "apple"));
$collection->insert(array("category" => "fruit", "name" => "peach"));
$collection->insert(array("category" => "fruit", "name" => "banana"));
$collection->insert(array("category" => "veggie", "name" => "corn"));
$collection->insert(array("category" => "veggie", "name" => "broccoli"));
$keys = array("category" => 1);
$initial = array("items" => array());
$reduce = "function (obj, prev) { prev.items.push(obj.name); }";
$g = $collection->group($keys, $initial, $reduce);
echo json_encode($g['retval']);
?>
Результатом выполнения данного примера будет что-то подобное:
[{"category":"fruit","items":["apple","peach","banana"]},{"category":"veggie","items":["corn","broccoli"]}]
Пример #2 MongoCollection::group() example
This example doesn't use any key, so every document will be its own group. It also uses a condition: only documents that match this condition will be processed by the grouping function.
<?php
$collection->save(array("a" => 2));
$collection->save(array("b" => 5));
$collection->save(array("a" => 1));
// use all fields
$keys = array();
// set intial values
$initial = array("count" => 0);
// JavaScript function to perform
$reduce = "function (obj, prev) { prev.count++; }";
// only use documents where the "a" field is greater than 1
$condition = array('condition' => array("a" => array( '$gt' => 1)));
$g = $collection->group($keys, $initial, $reduce, $condition);
var_dump($g);
?>
Результатом выполнения данного примера будет что-то подобное:
array(4) {
["retval"]=>
array(1) {
[0]=>
array(1) {
["count"]=>
float(1)
}
}
["count"]=>
float(1)
["keys"]=>
int(1)
["ok"]=>
float(1)
}
Пример #3 Passing a keys function
If you want to group by something other than a field name, you can pass a function as the first parameter of MongoCollection::group() and it will be run against each document. The return value of the function will be used as its grouping value.
This example demonstrates grouping by the num field modulo 4.
<?php
$c->group(new MongoCode('function(doc) { return {mod : doc.num % 4}; }'),
array("count" => 0),
new MongoCode('function(current, total) { total.count++; }'));
?>
- PHP Руководство
- Функции по категориям
- Индекс функций
- Справочник функций
- Расширения для работы с базами данных
- Расширения для работы с базами данных отдельных производителей
- MongoDB
- Базовые классы
- Функция MongoCollection::aggregate() - Perform an aggregation using the aggregation framework
- Функция MongoCollection::aggregateCursor() - Execute an aggregation pipeline command and retrieve results through a cursor
- Функция MongoCollection::batchInsert() - Inserts multiple documents into this collection
- Функция MongoCollection::__construct() - Creates a new collection
- Функция MongoCollection::count() - Counts the number of documents in this collection
- Функция MongoCollection::createDBRef() - Creates a database reference
- Функция MongoCollection::createIndex() - Creates an index on the specified field(s) if it does not already exist.
- Функция MongoCollection::deleteIndex() - Deletes an index from this collection
- Функция MongoCollection::deleteIndexes() - Delete all indices for this collection
- Функция MongoCollection::distinct() - Retrieve a list of distinct values for the given key across a collection.
- Функция MongoCollection::drop() - Drops this collection
- Функция MongoCollection::ensureIndex() - Creates an index on the specified field(s) if it does not already exist.
- MongoCollection::find
- Функция MongoCollection::findAndModify() - Update a document and return it
- Функция MongoCollection::findOne() - Queries this collection, returning a single element
- Функция MongoCollection::__get() - Gets a collection
- Функция MongoCollection::getDBRef() - Fetches the document pointed to by a database reference
- Функция MongoCollection::getIndexInfo() - Returns information about indexes on this collection
- Функция MongoCollection::getName() - Returns this collection's name
- Функция MongoCollection::getReadPreference() - Get the read preference for this collection
- Функция MongoCollection::getSlaveOkay() - Get slaveOkay setting for this collection
- Функция MongoCollection::getWriteConcern() - Get the write concern for this collection
- Функция MongoCollection::group() - Performs an operation similar to SQL's GROUP BY command
- Функция MongoCollection::insert() - Inserts a document into the collection
- Функция MongoCollection::parallelCollectionScan() - Returns an array of cursors to iterator over a full collection in parallel
- Функция MongoCollection::remove() - Remove records from this collection
- Функция MongoCollection::save() - Saves a document to this collection
- Функция MongoCollection::setReadPreference() - Set the read preference for this collection
- Функция MongoCollection::setSlaveOkay() - Change slaveOkay setting for this collection
- Функция MongoCollection::setWriteConcern() - Set the write concern for this database
- Функция MongoCollection::toIndexString() - Converts keys specifying an index to its identifying string
- Функция MongoCollection::__toString() - String representation of this collection
- Функция MongoCollection::update() - Update records based on a given criteria
- Функция MongoCollection::validate() - Validates this collection
Коментарии
Here I am posting how I get tags from my documents. Documents should have 'tags' field which is array of strings:{'tags':['php', 'mongo']}
<?php
$keys = array();
$initial = array('tags'=>array(), 'count'=>0);
$reduce = 'function (doc, total) { if (doc.tags.length) {doc.tags.forEach(function (e) {total.tags[e]=total.tags[e]||0; total.tags[e]++; total.count++;});} }';
$criteria = array(
'condition' => array(
'tags' => array('$exists'=>true)
),
);
?>
Here's my code to do an equivalent of a GROUP BY and a SUM
<?php
$contributionCol = $db->customers->contribution;
$group = $contributionCol->group(array('date' => true), array('sum' => 0), "function (obj, prev) { prev['sum'] += obj.amount; }");
?>
This groups by the 'date' column and sums over the 'amount' column. In my testing this was much slower than querying all rows and doing the Group by code with PHP. It could just be my particular setup and data set.
Also at first my amount column was a string, which caused the results to be concatenated rather than arithmetic addition, something else to watch out for.
[red.: Instead of this, please use the new aggregation framework. See the documentation for MongoCollection::aggregate]
Since the $options argument is no longer a scalar (deprecated since the 1.2.11 version of the Mongo's PHP driver), you now must compose your $options as an associative array, otherwise you'll rise a "Implicitly passing condition as $options will be removed in the future" alert.
Example:
<?php
$m = new Mongo();
$db = $m->selectDB('test');
$collection = new MongoCollection($db, 'FooBar');
// grouping results by categories, where foo is 'bar'
$keys = array('categorie'=>true, 'foo'=>true); // the fields list we want to return
$initial = array('count' => 0); // gets a subtotal for each categorie
$reduce = "function(obj,prev) { prev.count += 1; }"; // yes, this is js code
$conditions = array('foo'=> 'bar');
$grouped = $myColl::group($keys, $initial, $reduce, array('condition'=>$conditions));
$result = $grouped['retval'];
?>
quoting Evgeniy Abduzhapparov example for correction, since is not working on newest php mongo driver version
instead of use:
<?php
$initial = array('tags'=>array(), 'count'=>0);
?>
for var tags,
you have to cast the empty array to an object or use new stdClass()
<?php
$initial = array('tags'=> (object) array(), 'count'=>0);
$initial = array('tags'=> new stdClass(), 'count'=>0);
?>