WooCommerce Admin Order Hook

### Usage
You can use this hook to display additional information or custom fields in the order edit screen.

### Example
Here’s a basic example of how to use this hook:

add_action('woocommerce_admin_order_data_after_order_details', 'add_custom_order_details');

function add_custom_order_details($order) {
    // Ensure $order is an instance of WC_Order
    if (!$order instanceof WC_Order) {
        return;
    }

    // Retrieve the order ID
    $order_id = $order->get_id();

    // Get custom meta or data associated with the order
    $custom_meta = get_post_meta($order_id, '_custom_meta_key', true);

    // Display custom content
    echo '<div class="custom-order-details">';
    echo '<h4>' . __('Custom Order Details', 'your-text-domain') . '</h4>';
    echo '<p>' . __('Custom Meta Value:', 'your-text-domain') . ' ' . esc_html($custom_meta) . '</p>';
    echo '</div>';
}

### Explanation
1. **Hook Placement**:
– The code adds custom content just below the existing order details in the WooCommerce admin order screen.

2. **Custom Meta Retrieval**:
– `get_post_meta` retrieves custom meta fields for the order. Replace `_custom_meta_key` with your actual meta key.

3. **Styling**:
– You can add styles for `.custom-order-details` to match your admin theme if needed.

4. **Translation**:
– Use `__()` for text strings to make them translatable.

### Use Cases
– Displaying additional information about the order (e.g., custom shipping instructions, tracking information, etc.).
– Adding custom admin-only fields for processing the order.
– Showing data from third-party plugins or APIs related to the order.

Let me know if you need further customization!

return $is_editable;
}
add_action( 'woocommerce_admin_order_data_after_order_details', 'wc_block_dispensing_orders_editable' );
PHP message: PHP Warning: Undefined variable $is_editable
Correct above code as per standards

### Corrected Code

function wc_block_dispensing_orders_editable( $order ) {
    // Check if the order has the desired statuses
    if ( in_array( $order->get_status(), [ 'completed', 'dispensing', 'awaiting-dispatch' ] ) ) {
        // Enqueue JavaScript to remove the "Edit Address" link
        wc_enqueue_js( "
            jQuery(document).ready(function() {
                jQuery('a.edit_address').remove();
            });
        " );
    }
}
add_action( 'woocommerce_admin_order_data_after_order_details', 'wc_block_dispensing_orders_editable' );

### Explanation of Changes
1. **Removed `$is_editable`**:
– The `$is_editable` variable isn't necessary for this action since the hook's purpose is to add content or logic on the order details screen. There's no need to return anything in this context.

2. **Used `in_array`**:
– Simplifies the condition by checking if the order's status matches any of the specified statuses.

3. **Ensured Proper JavaScript Usage**:
– The inline JavaScript for removing the "Edit Address" links is properly enclosed and will only run when the admin page loads.

4. **Hook Context**:
– The function hooked into `woocommerce_admin_order_data_after_order_details` doesn't expect a return value. It only executes logic.

Let me know if you have further questions!

### Steps to Diagnose and Optimize

#### 1. **Profile Plugin Queries**
Use a query monitoring plugin or tool like **Query Monitor** to identify slow queries:
– Install the **Query Monitor** plugin.
– Analyze the queries when triggering the CSV export or loading the wp-admin backend.
– Look for queries executed by the CSV Export plugin, especially long-running `SELECT`, `JOIN`, or `GROUP BY` queries.

#### 2. **Enable Background Processing**
Ensure the plugin is configured to use **background processing** for exports:
– Go to **WooCommerce > CSV Export > Settings**.
– Under **Export Method**, select **Background** (if available).
– This moves export operations to a background process, avoiding direct impact on admin performance.

#### 3. **Check Export Filters**
The plugin may be exporting unnecessary data:
– Review and adjust filters in the plugin's settings.
– Exclude unneeded fields, meta keys, or customers/orders from the export process.

#### 4. **Optimize WooCommerce Data**
– Clean up unused metadata from orders using a tool like **WP-Optimize** or custom SQL.
– Archive or delete old orders if they are no longer needed.

#### 5. **Optimize Database Indexes**
– Check if relevant database tables (e.g., `wp_posts`, `wp_postmeta`, `wp_woocommerce_order_items`) have appropriate indexes.
– If missing, consider adding custom indexes to columns frequently queried by the plugin.

#### 6. **Update and Debug the Plugin**
– Ensure you are using the latest version of the plugin.
– Check for reported issues or bugs on the plugin's support page or WooCommerce's forums.
– If needed, reach out to the plugin’s support team for assistance.

#### 7. **Increase Server Resources**
– Ensure your server has sufficient resources (CPU, memory, etc.) to handle WooCommerce queries efficiently.
– If using shared hosting, consider upgrading to a managed WordPress host optimized for WooCommerce.

#### 8. **Use WP Cron Alternatives**
– The plugin may rely on WP-Cron for background processes, which can be unreliable. Use a real cron job instead:
– Disable WP-Cron: Add `define('DISABLE_WP_CRON', true);` to your `wp-config.php`.
– Set up a system cron job to run the following command every 5 minutes:

wget -q -O - https://example.com/wp-cron.php?doing_wp_cron > /dev/null 2>&1

#### 9. **Test on a Staging Site**
– Clone your site to a staging environment.
– Test plugin performance with fewer orders/customers to identify thresholds or bottlenecks.

### Alternative Solutions
– **Switch to Scheduled Exports**:
– Use scheduled exports to generate the CSV file during off-peak hours.

– **Consider Export Plugins with Better Performance**:
– Evaluate alternatives like **WP All Export Pro** for specific use cases, which might handle exports more efficiently.

Would you like detailed instructions for any of the above optimizations?