auto add jnews primaryu category to all posts (per 1000 post)

add_action(
    'admin_init',
    function () {
        if ( 'jnews' === $_GET['page'] && 'documentation' === $_GET['path'] ) {
            $args = array(
                'post_type'      => 'post',
                'posts_per_page' => 1000,
                'offset'         => 0, /* change offset every time until get all of your post */
            );

            $query = new WP_Query( $args );

            if ( $query->have_posts() ) {
                while ( $query->have_posts() ) {
                    $query->the_post();
                    $post_id  = get_the_ID();
                    $category = jnews_get_metabox_value( 'jnews_primary_category.id', null, $post_id );
                    if ( empty( $category ) ) {
                        $categories = array_slice( get_the_category( $post_id ), 0, 1 );
                        if ( ! empty( $categories ) ) {
                            $category    = array_shift( $categories );
                            $category_id = $category->term_id;
                            update_post_meta( $post_id, 'jnews_primary_category', array( 'id' => (int) $category_id ) );
                        }
                    }
                }
                wp_reset_postdata();
            }
        }
    }
);