In woocommerce, what determines the order_item_id? - unique

Question

I've got a webshop running with woocommerce. The webshop has products with variations. When I add the same product with the same variation, I want it to generate a new order_item_id, in stead of combining the two under the same order_item_id.
I can't seem to find the bit of code that is responsible for generating the order_item_id.
Could anyone tell me where this bit of code is located?
My goal is to make each product unique in stead of stacking items that are the same.
-EDIT
Ok, so I've narrowed it down to class-wc-cart.php
On line 782 the product ID is generated with the following code:
public function generate_cart_id( $product_id, $variation_id = '', $variation = '', $cart_item_data = array() ) {
$id_parts = array( $product_id );
if ( $variation_id ) $id_parts[] = $variation_id;
if ( is_array( $variation ) ) {
$variation_key = '';
foreach ( $variation as $key => $value ) {
$variation_key .= trim( $key ) . trim( $value );
}
$id_parts[] = $variation_key;
}
if ( is_array( $cart_item_data ) && ! empty( $cart_item_data ) ) {
$cart_item_data_key = '';
foreach ( $cart_item_data as $key => $value ) {
if ( is_array( $value ) ) $value = http_build_query( $value );
$cart_item_data_key .= trim($key) . trim($value);
}
$id_parts[] = $cart_item_data_key;
}
return md5( implode( '_', $id_parts ) );
}
Now all that is left is to edit in a unique ID via a timestamp or something.
Will keep you guys posted.

Answer 1

Solved it.
Open class-wc-cart.php, and add a timestamp, or anything else that is unique to $id_parts.
Just like in the following code:
public function generate_cart_id( $product_id, $variation_id = '', $variation = '', $cart_item_data = array() ) {
$id_parts = array( $product_id );
if ( $variation_id ) $id_parts[] = $variation_id.time();
if ( is_array( $variation ) ) {
$variation_key = '';
foreach ( $variation as $key => $value ) {
$variation_key .= trim( $key ) . trim( $value );
}
$id_parts[] = $variation_key.time();
}
if ( is_array( $cart_item_data ) && ! empty( $cart_item_data ) ) {
$cart_item_data_key = '';
foreach ( $cart_item_data as $key => $value ) {
if ( is_array( $value ) ) $value = http_build_query( $value );
$cart_item_data_key .= trim($key) . trim($value);
}
$id_parts[] = $cart_item_data_key.time();
}
return md5( implode( '_', $id_parts ) );
}