Hi Igor, As Misa points out, my original design used 2 tables - category & line-items. Either way it's two tables. The biggest difference lies in the approach to summing line-items by various levels of category - with each branch of the tree having different levels.
I cannot speak to performance, but understanding CTEs has been difficult for me. Ltree is so much simpler. I am certain there is a place for CTEs, but why torture myself trying to hash out a CTE when ltree makes the queries so much easier to write? On Feb 26, 2013 11:14 AM, "Misa Simic" <misa.si...@gmail.com> wrote: > > Hi Igor, > > I agree it is all "in the eyes of beholder". > > Would be good if you can show how to achieve the goal (Summing on Top Levels categories in hierarchy) with CTE? > > For example show all categories in level 2 (x), and sum amounts for each... (Sum takes all amounts from all transactions of its child categories in any bellow levels). > > I have tested both scenarios - and indexed ltree has given better result - though there is a possibility I haven't pick best approach to solve the problem with CTE... > > I am just interested in performance - implementation detail is less important... > > Data: > > Total number of categories: 1000 (in all levels) > No of Categories in top level: 5 > No of categories in level 2: 20 > Total number of levels: can vary - max in my testing was 8... > > > Transaction rows with amounts: 1 000 000 > > > (though I am not sure what u meant by: "2-table design using ltree", and with CTE there are 2 tables... Categories and Transactions: just in categories instead of ltree datatype, is integer datatype: parent_id) > > Many thanks, > > Misa > > > 2013/2/26 Igor Neyman <iney...@perceptron.com> >> >> >> >> From: Don Parris [mailto:parri...@gmail.com] >> Sent: Sunday, February 24, 2013 5:21 PM >> To: pgsql-sql@postgresql.org >> Subject: Using Ltree For Hierarchical Structures >> >> Hi all, >> With many thanks to Misa and others who helped out with my question about working with hierarchical data, I have now written a blog post on how I implemented the ltree module to solve my problem. >> >> http://dcparris.net/2013/02/24/using-ltree-hierarchical-postgresql/ >> Frankly, if you work with hierarchical data, I'm not sure I could recommend it strongly enough. I should think that even experienced, advanced SQL gurus would appreciate the simplicity ltree offers, when compared to the ugly table designs and recursive queries in order to work with hierarchical structures. >> I really hope this blog post will help others in the same boat. >> >> >> Regards, >> Don >> >> >> It's all "in the eyes of beholder". >> IMHO, recursive CTEs are perfect for hierarchical structures, and much cleaner than 2-table design using ltree, that you show in the blog. >> >> Regards, >> Igor Neyman >> >> >> >> >> -- >> Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) >> To make changes to your subscription: >> http://www.postgresql.org/mailpref/pgsql-sql > >
