Chunk set processing in Laravel

If you need to process thousands of Eloquent results, you can use the chunk command. The chunk method will get a "chunk" Eloquent model and populate it into the given closure for processing. Using the chunk method can effectively reduce memory consumption when processing large data collections:

Flight::chunk(200, function ($flights) {
    foreach ($flights as $flight) {
        //
    }
});

        $all_ark=Arkvolume::chunk(50000, function ($flights) {
            foreach ($flights as $flight) {
               $GLOBALS['something'][] = $flight['id'];
            }
        });

        var_dump($GLOBALS['something'] );exit;

This paragraph The code is to execute a 100-piece data update, and when the execution is completed, continue with another 100 pieces of data...
That is to say, each time he operates a data block instead of the entire database.

It should be noted that when using chunks with filtering conditions, if it is self-updating, you will miss some data. Next, look at the code:

##

User::where('approved', 0)->chunk(100, function ($users) {
  foreach ($users as $user) {
    $user->update(['approved' => 1]);
  }
});

If you want to run the above code, there will be no error, but the

where condition is to filter the user## that approved is 0 #Then update the value of approved to 1. In this process, after the data in the first database is modified, the data in the next data block will be selected from the modified data. At this time, the data has changed, and the page has also been increased by 1. Therefore, after the execution, only half of the data in the data has been updated.
If you don’t understand, let’s take a look at the underlying implementation of chunk. Taking the above code as an example, if there are 400 pieces of data in total, the data is divided into blocks according to 100 pieces.

page = 1: At the beginning, the page is 1, and 1-100 pieces of data are selected for processing;

page = 2: At this time, the
approved
values ​​of the first 100 pieces of data are all 1. Then in the first screening, the data will start from the 101st item, and at this time page=2, then the data processed will be the data before 200-300 and still after.

public function chunk($count, callable $callback)
{
    $results = $this->forPage($page = 1, $count)->get();

    while (count($results) > 0) {
        // On each chunk result set, we will pass them to the callback and then let the
        // developer take care of everything within the callback, which allows us to
        // keep the memory low for spinning through large result sets for working.
        if (call_user_func($callback, $results) === false) {
            return false;
        }

        $page++;

        $results = $this->forPage($page, $count)->get();
    }

    return true;
}

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