woocommerce/includes/class-wc-order-query.php

<?php
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Class for parameter-based Order querying.
 *
 * @version  3.1.0
 * @since    3.1.0
 * @package  WooCommerce/Classes
 * @category Class
 */
class WC_Order_Query extends WC_Object_Query {

	/**
	 * Valid query vars for orders.
	 * @return array
	 */
	protected function get_default_query_vars() {
		return array_merge(
			parent::get_default_query_vars(),
			array(
				'status'                => array_keys( wc_get_order_statuses() ),
				'type'                  => wc_get_order_types( 'view-orders' ),
				'currency'              => '',
				'version'               => '',
				'prices_include_tax'    => '',
				'date_created'          => '',
				'date_modified'         => '',
				'date_completed'        => '',
				'date_paid'             => '',
				'discount_total'        => '',
				'discount_tax'          => '',
				'shipping_total'        => '',
				'shipping_tax'          => '',
				'cart_tax'              => '',
				'total'                 => '',
				'total_tax'             => '',
				'customer_id'           => '',
				'order_key'             => '',
				'billing_first_name'    => '',
				'billing_last_name'     => '',
				'billing_company'       => '',
				'billing_address_1'     => '',
				'billing_address_2'     => '',
				'billing_city'          => '',
				'billing_state'         => '',
				'billing_postcode'      => '',
				'billing_country'       => '',
				'billing_email'         => '',
				'billing_phone'         => '',
				'shipping_first_name'   => '',
				'shipping_last_name'    => '',
				'shipping_company'      => '',
				'shipping_address_1'    => '',
				'shipping_address_2'    => '',
				'shipping_city'         => '',
				'shipping_state'        => '',
				'shipping_postcode'     => '',
				'shipping_country'      => '',
				'payment_method'        => '',
				'payment_method_title'  => '',
				'transaction_id'        => '',
				'customer_ip_address'   => '',
				'customer_user_agent'   => '',
				'created_via'           => '',
				'customer_note'         => '',
			)
		);
	}

	/**
	 * Get orders matching the current query vars.
	 * @return array of WC_Order objects
	 */
	public function get_orders() {
		$args = apply_filters( 'woocommerce_order_query_args', $this->get_query_vars() );
		$results = WC_Data_Store::load( 'order' )->query( $this->get_query_vars() );
		return apply_filters( 'woocommerce_order_query', $results, $args );
	}
}