WordPress at a glance
function is not described

update_post_thumbnail_cache() WP 3.2.0

Update cache for thumbnails in the current loop.

  • Global. WP_Query. $wp_query

No Hooks.

Return

Nothing (null).

Usage

update_post_thumbnail_cache( $wp_query );
$wp_query(WP_Query)
A WP_Query instance.
Default: $wp_query global

Code of update post thumbnail cache: wp-includes/post-thumbnail-template.php VER 5.0.3

<?php
function update_post_thumbnail_cache( $wp_query = null ) {
	if ( ! $wp_query )
		$wp_query = $GLOBALS['wp_query'];

	if ( $wp_query->thumbnails_cached )
		return;

	$thumb_ids = array();
	foreach ( $wp_query->posts as $post ) {
		if ( $id = get_post_thumbnail_id( $post->ID ) )
			$thumb_ids[] = $id;
	}

	if ( ! empty ( $thumb_ids ) ) {
		_prime_post_caches( $thumb_ids, false, true );
	}

	$wp_query->thumbnails_cached = true;
}