function wc_update_220_variations() {
	global $wpdb;
	// Update variations which manage stock.
	$update_variations = $wpdb->get_results(
		"SELECT DISTINCT posts.ID AS variation_id, posts.post_parent AS variation_parent FROM {$wpdb->posts} as posts
		LEFT OUTER JOIN {$wpdb->postmeta} AS postmeta ON posts.ID = postmeta.post_id AND postmeta.meta_key = '_stock'
		LEFT OUTER JOIN {$wpdb->postmeta} as postmeta2 ON posts.ID = postmeta2.post_id AND postmeta2.meta_key = '_manage_stock'
		WHERE posts.post_type = 'product_variation'
		AND postmeta.meta_value IS NOT NULL
		AND postmeta.meta_value != ''
		AND postmeta2.meta_value IS NULL"
	);

	foreach ( $update_variations as $variation ) {
		$parent_backorders = get_post_meta( $variation->variation_parent, '_backorders', true );
		add_post_meta( $variation->variation_id, '_manage_stock', 'yes', true );
		add_post_meta( $variation->variation_id, '_backorders', $parent_backorders ? $parent_backorders : 'no', true );
	}
}