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Re:Representing Trees in PostgreSQL by tempVariable on Friday November 21, 2014 @01:48PM (#8642626)
In addition to expensive insert/update, it is necessary to keep the left and right boundaries across ALL of your entries in perfect order. If the boundaries get out of whack, fixing the tree is a nightmare scenario.

I worked on a multi-tenant application with distinct trees present in one table and with one tree per table and so on. Fun fun fun!

Re:Representing Trees in PostgreSQL by alistairbayley on Friday November 21, 2014 @03:15PM (#8643169)
I think the nested intervals model, a refinement of nested sets, solves this slow update problem: http://www.rampant-books.com/art_vadim_nested_sets_sql_trees...

But I've never had to use it, so I am just guessing.

Same article, different site: https://communities.bmc.com/docs/DOC-9902

And a paper: http://www.sigmod.org/publications/sigmod-record/0506/p47-ar...

Here's a comparison of the different approaches in a matrix: http://vadimtropashko.wordpress.com/2008/08/09/one-more-nest...