Count entries in postgresql grouped by date

Hi!

I have a table with visits with a visited_at: attribute which is a
datetime
field. They seem to be stored as UTC. Now I want to count all visits
each
day and return something like:
{
2013-01-01: 8,
2013-01-02: 4,
2013-01-07: 9,

}

So, I did it like this which kind of works…:
def self.total_grouped_by_day(start_date, end_date)
visits = where(visited_at: start_date…end_date)
visits = visits.group(“date(visited_at)”)
visits = visits.select(“date(visited_at) as date, count(visits.id)
as
total_visits”)
visits = visits.order(“date ASC”)
visits.group_by { |v| v.date.to_date }
end

It doesn’t return exactly the format I want but that’s not the big
problem.
The problem is that if a visit happens near midnight it may be counted
at
the “wrong” date due to time zones. I understand why, because
“date(visited_at)” doesn’t know anything about my timezone.

Any good ideas on how to fix this issue?

I’ll just don’t do the group and count in the database for now. I do it
like this instead:

def self.total_grouped_by_day(start_date, end_date)
visits = where(visited_at: start_date…end_date)
visits = visits.order(“visited_at ASC”)
visits.group_by { |v| v.visited_at.to_date }
end

And then just use visits[date].count for the counting. There will
probably
not be that many records anyway…

Den tisdagen den 29:e januari 2013 kl. 17:26:00 UTC+1 skrev Linus
Pettersson:

You’re looking for the “AT TIME ZONE” construct.

On Jan 29, 2013, at 9:26 AM, Linus P. wrote:

So, I did it like this which kind of works…:
Any good ideas on how to fix this issue?


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Scott R.
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