I have a sql database that I query with ActiveRecord. (version of ActiveRecord is 4.2.5.1)
My query look like this:
User.
select('COUNT (DISTINCT user_id) as user_count').
select("date_trunc('month', created_at) as month").
select('city').
where('created_at > ?', 1.year.ago.utc.to_s(:db)).
group('month, city').
to_a.map do |row|
{
user_count: row.user_count,
month: row.month,
city: row.city
}
And I get results like this:
[
[ 0] {
:user_count => 165,
:month => 2015-09-01 00:00:00 UTC,
:city => "Paris"
},
[ 1] {
:user_count => 33,
:month => 2015-09-01 00:00:00 UTC,
:city => "Berlin"
},
...
]
And this is fine.
However, with this query:
User.
select('COUNT (DISTINCT user_id) as user_count').
select("date_trunc('month', created_at) as month").
select('city').
where('created_at > ?', 1.year.ago.utc.to_s(:db)).
group('month, city').
to_a
I get results like this:
[
[ 0] #<User:0x007facebac3560> {
:user_id => nil, # wtf is this
:city => "Paris"
# where is the month?
},
[ 1] #<User:0x007facebac33a8> {
:user_id => nil,
:city => "Berlin"
},
...
]
Which is not fine.
Why do I have to manually map the results even when I selected the rows I wanted?
Ideally, what I want is this:
User.
select(...).
where(...).
group(...).
to_array_of_hashes_with_the_keys_i_selected
Notice that if my query is a custom query, to_a does what I want, for example:
ActiveRecord::Base.connection.execute(<<~SQL
SELECT COUNT (DISTINCT user_id) as user_count, date_trunc('month', created_at) as month, city
FROM users
WHERE created_at > '2015-09-01 13:28:40'
GROUP BY month, city
SQL
).to_a # this is fine
From How to convert activerecord results into a array of hashes , I can do:
User.
select(...).
where(...).
group(...).
as_json
And I get
[
[ 0] {
"user_id" => nil,
"city" => "Paris",
"user_count" => 165,
"month" => 2015-09-01 00:00:00 UTC
},
...
Not exactly what I selected, but close enough.
.as_json.map{|e|e.except('user_id')}
gives me what I want
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