Do you have any website references to that?
On 8.12.2004, at 13:58, Richard Emberson wrote:
Forget Mr. Celko's work on nested sets - its old stuff. Look for
Vadim Tropashko's work on Farey Sequences and Continued Fractions -
a much improved way of creating trees with generic SQL.
Richard
Max Pfingsthorn wrote:
Dear Developers,
I was recently looking up different algorithms to store trees in an
SQL database. I have found these very interesting articles from 1996.
The author, Joe Celko, writes that trees can be represented as Nested
Sets (see the first article for some explanation). I think, this
might be useful to Slide's SQL backend and the querying of the WebDAV
tree. 'Recursive' searches, i.e. depth=infinity, reduce to mere
SELECTs comparing integers rather than making the DB match strings.
And, with a little extra, depth=1 is also a simple SELECT. However,
inserts are a bit more expensive, which would be fine, however, since
in general, the WebDAV repository is not written to so often in
comparison to the reads.
What do you think about restructuring the SQL to take advantage of
this?
For complete reference on the Nested Sets, see:
http://www.dbmsmag.com/9603d06.html
http://www.dbmsmag.com/9604d06.html
http://www.dbmsmag.com/9605d06.html
http://www.dbmsmag.com/9606d06.html
In general, I am very interested in optimizing the SQL backend a bit
more. I noticed that the LIMIT clause is actually emulated within the
backend instead of using the SQL feature. We are using MySQL behind
Slide, so that would help us a lot. What do you think about
specializing the backend(s) even more to take full advantage of the
different vendor-specific implementations? Of course, maintenance
would be harder, but it sure would give performance a kick.
Best regards,
Max Pfingsthorn
Hippo
Oosteinde 11
1017WT
Amsterdam
The Netherlands
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