Nested loop caused slow in performance - laravel

Question

foreach ($id_prs as $ids) {
list($id_pr, $id_cart) = explode('-', $ids);
foreach ($id_cart as $id) {
$r = Cart::find($id);
/// column to update value
$r->save();
}
}
This is how my loop looks like.
E.g. $id_prs consist of 10 data, while each id_prs may consist of 20 data etc.
From there, i found will take longer time to loop when a lots of data from each $id_cart.
How can i solve the performance issue, is there any solution?

Answer 1

This is known as n+1 problem, every time you iterate inside foreach additional query is created.
So this line is the evil, because it's querying data every iteration.
$r = Cart::find($id);
You can make it better like this:
$cart = Cart::all();
foreach ($id_prs as $ids) {
list($id_pr, $id_cart) = explode('-', $ids);
foreach ($id_cart as $id) {
// Get it from collection rather than query it from database
$cart->where('id', $id)->first()->save();
}
}
Where you acctualy query all carts inside variable as a collection, and you just manipulating with that collection localy without touching database (only when you hit save method).

Answer 2

Your code and variables are not clear enough. But a better solution is:
foreach ($id_prs as $ids) {
list($id_pr, $id_cart) = explode('-', $ids);
$items = Cart::whereIn('id', $id_cart) -> get();
foreach($items as $item) {
Cart::where('id', $item -> id) -> limit(1) -> update([
// Columns to update
]);
}
}

Answer 3

If you want to update same value for all the records
$allIds = [];
foreach ($id_prs as $ids) {
list($id_pr, $id_cart) = explode('-', $ids);
foreach ($id_cart as $id) {
$allIds[] = $id;
}
}
$cart = Cart::whereIn('id',$allIds)->update(['columns'=>'value']);