Get all post IDs from current WP_Query - not just currently visible

Question

I want to get all post IDs from the current query. I know how to get all IDs of the current page using the following:

global $wp_query;
$post_ids = wp_list_pluck( $wp_query->posts, "ID" ); 

This will give me an array of all post IDs, but limited to the current page.

How can I get all IDs but not limited by 'posts_per_page'. (I don't want to modify the query by changing 'posts_per_page'.)

I know that there is already information available from the global $wp_query such as:

We will be displaying " . $wp_query->query_vars['posts_per_page'] . " posts per page if possible.

We need a total of " . $wp_query->max_num_pages . " pages to display the results.

Additional Details:

I am trying to get WooCommerce product IDs and hooking into the woocommerce_archive_description action to do this.

Answer 1

Slightly old post I know but I just hit this exact issue myself.

Given a main_query find all the post IDs for it not limited by pagination.

I have made this function to return all terms for the main wp_query.

/*
 * Get terms for a given wp_query no paging
 * */
function get_terms_for_current_posts($tax='post_tag',$the_wp_query=false){
    global $wp_query;
    // Use global WP_Query but option to override
    $q = $wp_query;
    if($the_wp_query){
        $q = $the_wp_query;
    }

    $q->query_vars['posts_per_page'] = 200;// setting -1 does not seem to work here?
    $q->query_vars['fields'] = 'ids';// I only want the post IDs
    $the_query = new WP_Query($q->query_vars);// get the posts
    // $the_query->posts is an array of all found post IDs
    // get all terms for the given array of post IDs
    $y = wp_get_object_terms( $the_query->posts, $tax );
    return $y;// array of term objects
}

Hope this helps you or someone else stumbling across this.

Answer 2

Wanted to share my two cents.

Indeed, the main $wp_query will only return the posts correlating to the current Pagination Parameters.

Like Milo pointed out in the comments you can actually create a new query with a different set of pagination parameters (eg: nopaging, posts_per_page, posts_per_archive_page ...).

We can mirror the main query parameters and merge them with our new pagination parameters. As we're only interested in the posts ids, we can use the fields query parameter to only return the posts ids.

/**
 * Retrieve the IDs of the items in the main WordPress query.
 * 
 * Intercept the main query, retrieve the current parameters to create a new query.
 * Return the IDs of the items in the main query as an array.
 * 
 * @see https://wordpress.stackexchange.com/a/400947/190376
 * 
 * @return Array The IDs of the items in the WordPress Loop. False if $post is not set.
 * 
 * @since 1.0.0
 */
public function wpso_323280() {

    if ( is_main_query() ) {

        global $wp_query;

        $buffer_query = $wp_query->query;
    
        $args = array(
            'nopaging' => true,
            'fields' => 'ids',
        );
    
        $custom_query = new WP_Query( array_merge( $buffer_query, $args ) );
    
        wp_reset_postdata();
    
        return $custom_query->posts;

    };

}