Well, in jforum_posts the post_id is an auto_increment in fact, as well the topic_id in jforum_topics, But the relationship between them is done via SQL or
Java code. So, for each jforum_topic where are one to many jforum_posts. You can take a look at src/net/jforum/view/forum/PostAction.java, src/net/jforum/drivers/generic/PostModel.java and src/net/jforum/drivers/generic/TopicModel.java.
Rafael
[originally posted on jforum.net by Rafael Steil]