Two orders double-counted in WooCommerce Analytics

Just a quick update for the readers to inform that we found the quirk that causes the data duplication. It’s actually linked to the WooCommerce core. We have a piece of logic that changed slightly. Here’s an example of what changed, simplified for easier understanding:

add_action('woocommerce_after_order_object_save', function(WC_Order $order) {
  $exchange_rate = get_exchange_rate();
  $order->update_meta_data('_order_total_base_currency', $order->get_total() * $exchange_rate);
  $order->update_meta_data('_order_total_tax_base_currency', $order->get_total_tax() * $exchange_rate);
  // Save more meta, converting order properties

   // Save the exchange rate last
  $order->update_meta_data('_base_currency_exchange_rate', $exchange_rate);
  $order->save_meta_data();
});

To this:

add_action('woocommerce_after_order_object_save', function(WC_Order $order) {
  $exchange_rate = get_exchange_rate();
   // Save the exchange rate first
  $order->update_meta_data('_base_currency_exchange_rate', $exchange_rate);

  $order->update_meta_data('_order_total_base_currency', $order->get_total() * $exchange_rate);
  $order->update_meta_data('_order_total_tax_base_currency', $order->get_total_tax() * $exchange_rate);
  // Save more meta, converting order properties

  $order->save_meta_data();
});

For reasons that I can’t explain, if action woocommerce_after_order_object_save is triggered more than once, the behaviour will be different in the two cases:

1. In the first case, the call to $order->update_meta_data('_base_currency_exchange_rate', $exchange_rate); adds the meta the first time and updates it the second time.
2. In the second case, the call to $order->update_meta_data('_base_currency_exchange_rate', $exchange_rate); adds the meta twice, resulting in data duplication.

We couldn’t figure out the reason behind this inconsistent behaviour. The only speculation, which hasn’t been proven, is that calling the WC_Order::get_total(), WC_Order::get_total_tax() and so on causes the custom meta set by WC_Order::update_meta_data() to be “forgotten”, so to speak, despite the call to WC_Order::save_meta_data(). I’m aware that it doesn’t make much sense, but the test results are consistent. Saving the exchange rate last doesn’t cause any duplication, for some reason.

We’re now implementing a safeguard, so that the meta won’t be duplicated despite this unexpected behaviour.

Additional note
So far, we’ve only noticed this behaviour on a site with the HPOS feature disabled, where the orders are stored in the wp_posts table. With the HPOS feature enabled, this doesn’t seem to happen. However, we will run more tests to check if that actually makes a difference.

• This reply was modified 1 year, 1 month ago by Diego. Reason: Added note about HPOS

@hansderuiter thanks for your feedback. It’s curious, because we haven’t been able to trigger the issue on any of our test servers, with our without the HPOS feature enabled. On a customer’s site, it only occurs with the HPOS feature disabled.

It looks like there is some other element that comes into play, and the fact that the condition in which the glitch occurs is so “nonsensical” is curious to say the least. In any case, the fix we put together is working, so the error should be prevented for the time being.

Hello Diego,

Thank you for sharing this update.

It’s great to hear about the safeguard in place.
Looking forward to seeing how the update performs and hoping it effectively resolves the issue.

Have a great day!