Problem with dates in Postgresql and Rails

Question

I want to do the following: Find all articles with where Time.now is between article.due_date and article.due_date - 8.hours. I'm having a lot of trouble trying to get it right. Any help would be much appreciated.

Thanks!

What is it that you are having problems with?

Jimmy Stenke
– Jimmy Stenke

2011-03-07 18:23:20 +00:00
Commented Mar 7, 2011 at 18:23 — Jimmy Stenke
– Jimmy Stenke, Commented Mar 7, 2011 at 18:23

jdl · Accepted Answer · 2011-03-07 18:53:30Z

1

Who said that algebra was worthless?

The two conditions you stated in your question.

T <= DUE
T >= DUE - 8h

Are the same as these two conditions.

DUE >= T
DUE <= T + 8h

You can apply now apply this to a query and/or scope without having to do datetime gymnastics in your database.

named_scope :near_due, lambda {{ :conditions => ["due_date >= ? AND due_date <= ?", Time.now, Time.now + 8.hours] }}

answered Mar 7, 2011 at 18:53

jdl

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2 Comments

Dave G Over a year ago

Ha. I just solved this myself. Had to relookup the rules for inequalities. Probably don't need the lambda unless we're passing the hours, which may indeed be a good idea. Have an accepted answer for your work though :)

jdl Over a year ago

You definitely need the lambda, otherwise Time.now will only be evaluated the first time your model is cached.

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