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how the fuck
i unsubscribe to this mailing list , i get more than 100 emails a day
Bye
From: Paul Jungwirth <pj@xxxxxxxxxxxxxxxxxxxxxxxx>
Sent: Wednesday, June 20, 2018 2:31 AM To: pgsql-general@xxxxxxxxxxxxxxxxxxxx Subject: Re: Is postorder tree traversal possible with recursive CTE's? On 06/19/2018 02:05 PM, Alban Hertroys wrote:
> On the more theoretical front: The question remains whether it is possible to calculate fields in post-order tree traversal. I think that would be a semantically proper way to express this type of problem and it wouldn't need the kinds of pre/post-processing that after-the-fact aggregation (like in above solution) requires. So, leaner, and probably faster. > That implies that the SQL committee thought of the possibility in the first place though, which I'm beginning to doubt... If this interests you, you might enjoy this StackOverflow question: https://stackoverflow.com/questions/35956486/generate-nested-json-with-couting-in-postgresql Briefly, how do you construct a nested JSON structure from a recursive CTE? The only answers at that link rely on plpgsql, but of course that is cheating. :-) I took a stab at it a couple years ago but couldn't figure it out, and it seemed like post-order processing was exactly the missing piece. If anyone has any ideas I'd be intrigued to hear them! -- Paul ~{:-) pj@xxxxxxxxxxxxxxxxxxxxxxxx |
