Implements a simplistic version of the popular Map-Reduce algorithm. Acts like an iterator for the original passed data after each result has been processed, thus offering a transparent wrapper for results coming from any source.
intCount of elements emitted during the Reduce phase
\TraversableHolds the original data that needs to be processed
boolWhether the Map-Reduce routine has been executed already on the data
arrayHolds the shuffled results that were emitted from the map phase
callableA callable that will be executed for each record in the original data
callable|nullA callable that will be executed for each intermediate record emitted during the Map phase
arrayHolds the results as emitted during the reduce phase
Runs the actual Map-Reduce algorithm. This is iterate the original data and call the mapper function for each , then for each intermediate bucket created during the Map phase call the reduce function.
Appends a new record to the final list of results and optionally assign a key for this record.
Appends a new record to the bucket labelled with $key, usually as a result of mapping a single record from the original data.
Returns an iterator with the end result of running the Map and Reduce phases on the original data
__construct(\Traversable $data, callable $mapper, ?callable $reducer)
Constructor
Separate all unique odd and even numbers in an array
$data = new \ArrayObject([1, 2, 3, 4, 5, 3]);
$mapper = function ($value, $key, $mr) {
$type = ($value % 2 === 0) ? 'even' : 'odd';
$mr->emitIntermediate($value, $type);
};
$reducer = function ($numbers, $type, $mr) {
$mr->emit(array_unique($numbers), $type);
};
$results = new MapReduce($data, $mapper, $reducer); Previous example will generate the following result:
['odd' => [1, 3, 5], 'even' => [2, 4]]
\Traversable $data the original data to be processed
callable $mapper the mapper callback. This function will receive 3 arguments. The first one is the current value, second the current results key and third is this class instance so you can call the result emitters.
callable|null $reducer optional the reducer callback. This function will receive 3 arguments. The first one is the list of values inside a bucket, second one is the name of the bucket that was created during the mapping phase and third one is an instance of this class.
_execute()
Runs the actual Map-Reduce algorithm. This is iterate the original data and call the mapper function for each , then for each intermediate bucket created during the Map phase call the reduce function.
LogicExceptionemit(mixed $val, mixed $key)
Appends a new record to the final list of results and optionally assign a key for this record.
mixed $val The value to be appended to the final list of results
mixed $key optional and optional key to assign to the value
emitIntermediate(mixed $val, mixed $bucket)
Appends a new record to the bucket labelled with $key, usually as a result of mapping a single record from the original data.
mixed $val The record itself to store in the bucket
mixed $bucket the name of the bucket where to put the record
getIterator()
Returns an iterator with the end result of running the Map and Reduce phases on the original data
\TraversableCount of elements emitted during the Reduce phase
intHolds the original data that needs to be processed
\TraversableWhether the Map-Reduce routine has been executed already on the data
boolHolds the shuffled results that were emitted from the map phase
arrayA callable that will be executed for each record in the original data
callableA callable that will be executed for each intermediate record emitted during the Map phase
callable|nullHolds the results as emitted during the reduce phase
array
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https://api.cakephp.org/4.1/class-Cake.Collection.Iterator.MapReduce.html