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.
$_counter protected integer$_data protected Traversable|null$_executed protected boolean$_intermediate protected arrayHolds the shuffled results that were emitted from the map phase
$_mapper protected callable$_reducer protected callableA callable that will be executed for each intermediate record emitted during the Map phase
$_result protected arrayRuns 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 null )
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]]
$data $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.
$reducer optional null 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.
if emitIntermediate was called but no reducer function was provided
emit( mixed $value , string|null $key null )
Appends a new record to the final list of results and optionally assign a key for this record.
$value $key optional null emitIntermediate( mixed $value , string $bucket )
Appends a new record to the bucket labelled with $key, usually as a result of mapping a single record from the original data.
$value $bucket getIterator( )
Returns an iterator with the end result of running the Map and Reduce phases on the original data
IteratorAggregate::getIterator() protected boolean
Whether the Map-Reduce routine has been executed already on the data
false
protected array
Holds the shuffled results that were emitted from the map phase
[]
protected callable
A callable that will be executed for each record in the original data
protected callable
A callable that will be executed for each intermediate record emitted during the Map phase
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https://api.cakephp.org/3.4/class-Cake.Collection.Iterator.MapReduce.html