I'm trying to store hierarchical data using SQLite. After searching a lot, I chose to use the nested set model instead of an adjacency list, because almost 90% of the operations will be reads and only 10% will be updates/deletes/creates.
I followed this example: http://www.phpro.org/tutorials/Managing-Hierarchical-Data-with-PHP-and-MySQL.html
And it works fine to add, delete and read new nodes.
But I didn't find any article explaining how to update the tree, e.g. moving a category into another category.
Below is my database structure:
id name left_node right_node
1 name1 1 2
** I didn't find a place explaining how to update the hierarchy, which I really need. **
Another problem is
public function delete_node($pleft, $pright){
$width = $pright-$pleft+1;
$delete_sql = "delete from categories where left_node between $pleft and $pright";
$update_sql1 = "update categories set right_node = right_node-$width where right_node > $pright";
$update_sql2 = "update categories set left_node = left_node-$width where left_node> $pright";
//
$this->db->trans_start();
//
$this->db->query($delete_sql);
//
$this->db->query($update_sql1);
$this->db->query($update_sql2);
$this->db->trans_complete();
//
return $this->db->trans_status();
}
This my delete method, and it takes 30ms to finish. Is that normal?
I solved the problem, thanks for the help http://www.ninthavenue.com.au/how-to-move-a-node-in-nested-sets-with-sql
I'm using codeigniter with sqlite database. below is my function,
public function move_node($pleft, $pright, $origin_left_pos, $origin_right_pos){
//
//the new_left_position is different according to which way you want to move the node
$new_left_position = $pleft + 1;
//
$width = $origin_right_pos - $origin_left_pos + 1;
$temp_left_position = $origin_left_pos;
$distance = $new_left_position - $origin_left_pos;
//backwards movement must account for new space
if($distance < 0){
$distance -= $width;
$temp_left_position += $width;
}
//
$update_sql1 = "update categories set left_node = left_node+$width where left_node >= $new_left_position";
$update_sql2 = "update categories set right_node = right_node+$width where right_node >= $new_left_position";
//
$update_sql3 = "update categories set left_node = left_node+$distance , right_node = right_node+$distance where left_node >= $temp_left_position AND right_node < $temp_left_position+$width";
//
$update_sql4 = "update categories set left_node = left_node-$width where left_node > $origin_right_pos";
$update_sql5 = "update categories set right_node = right_node-$width where right_node > $origin_right_pos";
//
$this->db->trans_start();
$this->db->query($update_sql1);
//
$this->db->query($update_sql2);
$this->db->query($update_sql3);
$this->db->query($update_sql4);
$this->db->query($update_sql5);
$this->db->trans_complete();
return $this->db->trans_status();
}
