posts_nav_link pulling in multiple post types

Question

I have an archive-regularproducts.php set up that looks like so:
PHP:

    <?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>
    //content goes here
    <?php endwhile; endif; ?>

    <?php wp_reset_query(); ?>

    <?php query_posts( 'post_type=wpsc-product'); ?>
        <?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>
        //content goes here
        <?php endwhile; endif; ?>

    <?php wp_reset_query(); ?>

    <nav id="page_nav">
        <?php posts_nav_link( ' ', ' ', ' '); ?>
    </nav>

As you can see I'm also querying the wpsc-product post type on this archive page too, the posts display fine, but as I'm using infinite scroll, when it gets to the bottom and pulls in the next page of posts, it's pulling in duplicate wpsc-product posts, thus I was wondering if there was a way to either have the posts_nav_link function for only the regularproducts post type, or a generally better way of achieving what I'm trying to achieve. Any suggestions would be greatly appreciated!

Answer 1

query_posts should be avoided at all costs. This is not just my emphasis, but the codex's as well

Note: This function isn't meant to be used by plugins or themes. As explained later, there are better, more performant options to alter the main query. query_posts() is overly simplistic and problematic way to modify main query of a page by replacing it with new instance of the query. It is inefficient (re-runs SQL queries) and will outright fail in some circumstances (especially often when dealing with posts pagination).

You should also have a look at this post for further explanation

You should use WP_Query in this instance.

<?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>
//content goes here
<?php endwhile; endif; ?>

<?php wp_reset_postdata(); ?>

<?php $my_query = new WP_Query( 'post_type=wpsc-product'); ?>
    <?php if ( $my_query->have_posts() ) : while ( $my_query->have_posts() ) : $my_query->the_post(); ?>
    //content goes here
    <?php endwhile; endif; ?>

<?php wp_reset_postdata(); ?>

<nav id="page_nav">
    <?php posts_nav_link( ' ', ' ', ' '); ?>
</nav>

Answer 2

Automatic pagination is only applied to the main query by default. Thus, the pagination is already working as it should. The problem probably lies in the way you're using InfiniteScroll.

IS allows you to target the container and items by a selector you specify. I would suggest wrapping the main query in a div and targeting that with Infinite Scroll. Are you using a plugin or implementing IS manually?

<div id="main">
    <?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>
        //content goes here
    <?php endwhile; endif; ?>
</div>

<?php wp_reset_query(); ?>

<?php query_posts( 'post_type=wpsc-product'); ?>
<?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>
    //content goes here
<?php endwhile; endif; ?>

<?php wp_reset_query(); ?>

<nav id="page_nav">
    <?php posts_nav_link( ' ', ' ', ' '); ?>
</nav>

Then, you should target the container #main and all post items inside it.