WordPress at a glance
function is not described

update_post_cache() WP 1.5.1

Updates posts in cache.

No Hooks.

Return

Nothing (null).

Usage

update_post_cache( $posts );
$posts(array) (required) (passed by reference — &)
Array of post objects (passed by reference).

Code of update post cache: wp-includes/post.php WP 5.2.2

<?php
function update_post_cache( &$posts ) {
	if ( ! $posts ) {
		return;
	}

	foreach ( $posts as $post ) {
		wp_cache_add( $post->ID, $post, 'posts' );
	}
}