How to sort WP Query by meta key exist or that meta value is equal one

Question

I have filter page which is contains all the product list, And i have two option first once is latest another one is featured. In database the post meta storing as is_feature = 1. During wp_query its only fetching is feautre =1. Actually i need data as like is_feature = 1 from starting ,which post doesn't have is_feature = '' or doesn't is_feature meta key, they need to display later is_feature = 1.

This is my query:

    $conditions = array( 
              'posts_per_page' => 9, 
              'paged' => $paged,   
              'post_type'   => 'custom',
              'meta_key' => 'is_feature',
              'order_by' => 'meta_key=is_feature',
              'order'            => 'DESC',
              'post_status' => "publish", )

    $the_query = new WP_Query( $conditions ); 

Answer 1

Replace order_by to orderby. Use meta_value as orderby parameter:

$conditions = array( 
    'posts_per_page' => 9, 
    'paged'          => $paged,   
    'post_type'      => 'custom',
    'meta_key'       => 'is_feature',
    'orderby'        => 'meta_value',
    'order'          => 'DESC',
    'post_status'    => "publish"
);

https://developer.wordpress.org/reference/classes/wp_query/#order-orderby-parameters