[BioSQL-l] left_value and right_value in taxon table
Hilmar Lapp
hlapp at gmx.net
Fri Apr 4 18:40:56 EDT 2008
Hi Eric,
On Apr 4, 2008, at 9:43 AM, Eric Gibert wrote:
> Dear all,
>
> I hope that I am not the 100th persons asking the following questions:
> 1) what are left and right values in the taxon table for?
they hold the nested set values. Nested sets are enumeration
algorithm described in Joe Celko's SQL for Smarties books, and Aaron
Mackey gives a good introduction here:
http://www.oreillynet.com/pub/a/network/2002/11/27/bioconf.html
(This is in the schema DDL file, though obviously should be
documented better. Good candidate for an FAQ, I suppose.)
> 2) How are they computed
load_ncbi_taxonomy.pl recomputes them automatically after each
update. It's a simple recursive depth-first graph traversal algorithm.
-hilmar
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