为什么求和大数据不起作用？ （Laravel 5.3）

Question

My code, you can see this below :

public function total()
{
    $query = User::limit(100000)->get();
    $total = $query->sum('total');
    dd($total);
}

The result of dd($total) not display or empty

But when I change limit(50000), it display the result

Why it does not work if limit(100000)?

Note :

In firefox browser, it does not display anything

In chrome browser, it display error :

This page isn’t working

myshop.dev is currently unable to handle this request. HTTP ERROR 500

Answer 1

When you call get, you are fetching all this records from the database. And then performing the sum with php. You are probably having a timeout when fetching that much records from the database.

Why don't you perform the sum in the database, and then fetch the result?

public function total()
{
    $total = User::limit(100000)->sum('total');
    dd($total);
}

----- edit -----

When you perform:

$query = User::limit(100000)->get();

The $query variable actually holds the result set of the query select * from user limit 100000. The result set its a collection (see collect), then you are performing a sum on the server-side, something equivalent to:

$sum = 0;
foreach ($user in $query) {
    $sum = $sum + $user->total;
}

It's better to perform the sum in the database using the proper aggregate function.

$total = User::limit(100000)->sum('total'); would translate to:

select SUM(total) from user limit 1000000

If the result is 0, probably all your result set for the column total is actually 0.