Source

File: wp-includes/comment.php

function _prime_comment_caches( $comment_ids, $update_meta_cache = true ) {
	global $wpdb;

	$non_cached_ids = _get_non_cached_ids( $comment_ids, 'comment' );
	if ( ! empty( $non_cached_ids ) ) {
		$fresh_comments = $wpdb->get_results( sprintf( "SELECT $wpdb->comments.* FROM $wpdb->comments WHERE comment_ID IN (%s)", join( ',', array_map( 'intval', $non_cached_ids ) ) ) );

		update_comment_cache( $fresh_comments, $update_meta_cache );
	}
}