Обсуждение: Common table expressions and threaded comments
Greetings, I need to implement the classical problem of threaded comments in a Postgresql database. I know that the upcoming 8.4 release includes Common Table Expressions, so I have to ask: is this feature the mother-of-all-solutions to the threaded comments problem, or is it still worth investigating ltree? Also, lots of people mention Joe Celko's book on this subject. Is it still a valid resource, or do CTE's make it obsolete? Thank you! C.S.
On Fri, Apr 17, 2009 at 1:40 PM, Cultural Sublimation <cultural_sublimation@yahoo.com> wrote: > > Greetings, > > I need to implement the classical problem of threaded comments in a Postgresql > database. I know that the upcoming 8.4 release includes Common Table > Expressions, so I have to ask: is this feature the mother-of-all-solutions > to the threaded comments problem, or is it still worth investigating ltree? > > Also, lots of people mention Joe Celko's book on this subject. Is it still > a valid resource, or do CTE's make it obsolete? Depending on what you actually need, but yes - CTE is the solution, depending obviously on your schema design... I think David (Fetter) had some examples in his slides on how to solve common problems like that in a query. -- GJ
Cultural Sublimation <cultural_sublimation@yahoo.com> writes:
> I need to implement the classical problem of threaded comments in a Postgresql
> database. I know that the upcoming 8.4 release includes Common Table
> Expressions, so I have to ask: is this feature the mother-of-all-solutions
> to the threaded comments problem, or is it still worth investigating ltree?
I don't think you should take CTEs as being the be-all and end-all of
solutions in this area (or any other). In particular I'd be suspicious
about the performance of a CTE-based solution. CTEs are new in 8.4 and
we have done essentially zero optimization work on them. I honestly
doubt if they will be able to match the performance of a single-purpose
solution such as ltree, even after a few years of optimization work.
regards, tom lane
I can only say for my own little experience. Features like that, allow users to exchange less (none?) data between app and pg. That's the main advantage of CTE.