apply_filters( 'woocommerce_shop_order_search_fields' )
Searches on meta data can be slow – this lets you choose what fields to search.
Description Description
3.0.0 added _billing_address and _shipping_address meta which contains all address data to make this faster. This however won’t work on older orders unless updated, so search a few others (expand this using the filter if needed).
Source Source
File: includes/data-stores/class-wc-order-data-store-cpt.php