Count all comments of a custom post type

Question

I know how to count comment per post, user and in total but i am
having problems getting the total amount of comments post in a specific post type.

I guess i can loop trough all the posts and count each one
comments but i am looking for something faster and less
resource expensive

Appreciate your help

I got this so far (i think this is a bad way but i might be wrong):

/*** ALL COMMENTS COUNT BY POST TYPE ***/
function countCptCommentsTotal() {

    // FAQ ARGS
    $faqStatsArgs = array(
        'post_type'         =>  'some_post_type',
        'post_status'       =>  'publish',
        'posts_per_page'    =>  -1
    );
    $faqstats_query = new WP_Query($faqStatsArgs);

    // THE LOOP
    $allAnswers = 0;
    while ($faqstats_query->have_posts()) {
        $faqstats_query->the_post();

        $curfaqid       =   get_the_ID();
        $allAnswers =   $allAnswers + countPostComments($curfaqid);

    }

    wp_reset_query();
    return $allAnswers;
}

Answer 1

How about direct sql with a simple subquery to first get all the post ids of your custom post type ex:

function get_all_comments_of_post_type($post_type){
  global $wpdb;
  $cc = $wpdb->get_var("SELECT COUNT(comment_ID)
    FROM $wpdb->comments
    WHERE comment_post_ID in (
      SELECT ID 
      FROM $wpdb->posts 
      WHERE post_type = '$post_type' 
      AND post_status = 'publish')
    AND comment_approved = '1'
  ");
  return $cc;
}

Usage:

$total_comments =  get_all_comments_of_post_type('some_post_type');

Answer 2

Simply do a plain MySQL Query that sums the comment_count row. The following plugin as an example:

<?php
namespace WPSE;

/**
 * Plugin Name: (#134338) Get total Comment Count
 * Plugin URl:  http://wordpress.stackexchange.com/q/134338
 */

defined( 'ABSPATH' ) or exit;

function commentCountTotal( $postType = 'post' )
{
    global $wpdb;
    return $wpdb->query( $wpdb->prepare(
        "SELECT sum( comment_count )
        FROM (
            SELECT comment_count
            FROM {$wpdb->posts}
            WHERE post_type = '%s'
            AND post_status = 'publish'
            AND comment_count > 0
            LIMIT 0 , 999
        ) as count",
        $postType
    ) );
}

You can then just call it to display the total amount of this post type.

echo \WSPE\commentCountTotal( 'your-post-type' );