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https://github.com/codesnik/calculate-all

calculate_all method for aggregate functions in Active Record
https://github.com/codesnik/calculate-all

activerecord aggregate average groupdate median mysql postgres rails statistics

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calculate_all method for aggregate functions in Active Record

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README 

        
# CalculateAll



Provides the `#calculate_all` method for your Active Record models, scopes and relations.

It's a small addition to Active Record's `#count`, `#maximum`, `#minimum`, `#average`, `#sum`

and `#calculate`.

It allows you to fetch all of the above, as well as other aggregate function results,

in a single request, with support for grouping.



Should be useful for dashboards, timeseries stats, and charts.



Currently tested with PostgreSQL, MySQL and SQLite3, ruby >= 2.6, rails >= 4, groupdate >= 4.



With rails >= 7.1, `#async_calculate_all` is also available, which does the same but in a separate

db connection and ruby thread, and returns `ActiveRecord::Promise`



## Usage



(example SQL snippets are given for PostgreSQL)



```ruby

stats = Order.group(:department_id).group(:payment_method).order(:payment_method).calculate_all(

  :payment_method,

  :count,

  :price_max,

  :price_min,

  :price_avg,

  total_users: :count_distinct_user_id,

  price_median: "percentile_cont(0.5) within group (order by price asc)",

  plan_ids: "array_agg(distinct plan_id order by plan_id)",

  earnings: "sum(price) filter (where status = 'paid')"

)

#   Order Pluck (20.0ms)  SELECT "orders"."department_id", "payment_method", COUNT(*), MAX(price), MIN(price), AVG(price),

#        COUNT(DISTINCT user_id), percentile_cont(0.5) within group (order by price asc),

#        array_agg(distinct plan_id order by plan_id), sum(price) filter (where status = 'paid')

#      FROM "orders" GROUP BY "orders"."department_id", "payment_method" ORDER BY "payment_method" ASC

# => {

#   [1, "card"] => {

#     payment_method: "card",

#     count: 10,

#     price_max: 500,

#     price_min: 100,

#     price_avg: 0.3e3,

#     total_users: 5,

#     price_median: 0.4e3,

#     plan_ids: [4, 7, 12],

#     earnings: 2340

#   },

#   [1, "cash"] => {

#     ...

#   }

# }

```



```ruby

stats_by_department = Order.group(:department_id).async_calculate_all(:count, :price_sum)

# continue with some other expensive stuff



# later, in some view

stats_by_department.value.each do |department_id, stats|

   # ...

end

```



## Rationale



Active Record makes it really easy to use most common database aggregate functions like COUNT(), MAX(), MIN(), AVG(), SUM().

But there's a whole world of other aggregate functions in

[PostgreSQL](http://www.postgresql.org/docs/current/functions-aggregate.html),

[MySQL](https://dev.mysql.com/doc/refman/9.3/en/aggregate-functions.html)

and [SQLite](https://www.sqlite.org/lang_aggfunc.html)

which I can’t recommend enough, especially if you’re working with statistics or business intelligence.



Also, in many cases, you’ll need multiple metrics at once. Typically, the database performs a full scan of the table for each metric.

However, it can calculate all of them in a single scan and a single request.



`#calculate_all` to the rescue!



## Arguments



`#calculate_all` accepts a single SQL expression with aggregate functions,



```ruby

  Model.calculate_all('CAST(SUM(price) as decimal) / COUNT(DISTINCT user_id)')

```



or arbitrary symbols and keyword arguments with SQL snippets, aggregate function shortcuts or previously given grouping values.



```ruby

  Model.group(:currency).calculate_all(

    :average_price, :currency, total: :sum_price, average_spendings: 'SUM(price)::decimal / COUNT(DISTINCT user_id)'

  )

```



For convenience, `calculate_all(:count, :avg_column)` is the same as `calculate_all(count: :count, avg_column: :avg_column)`



Here's a cheatsheet of recognized shortcuts:



| symbol                                                                 | would fetch

|------------------------------------------------------------------------|------------

| `:count`                                                               | `COUNT(*)`

| `:count_column1`, `:column1_count`                                     | `COUNT(column1)` (doesn't count NULL's in that column)

| `:count_distinct_column1`, `:column1_distinct_count`                   | `COUNT(DISTINCT column1)`

| `:max_column1`, `:column1_max`, `:maximum_column1`, `:column1_maximum` | `MAX(column1)`

| `:min_column1`, `:column1_min`, `:minimum_column1`, `:column1_minimum` | `MIN(column1)`

| `:avg_column1`, `:column1_avg`, `:average_column1`, `:column1_average` | `AVG(column1)`

| `:sum_column1`, `:column1_sum`                                         | `SUM(column1)`



Other functions are a bit too database specific, and are better to be given with an explicit SQL snippet.



Please don't put values from unverified sources (like HTML form or javascript call) into expression list,

it could result in malicious SQL injection.



## Result



`#calculate_all` tries to mimic magic of Active Record's `#group`, `#count` and `#pluck`

so result type depends on arguments and on groupings.



If you have no `group()` on underlying scope, `#calculate_all` will return just one row.



```ruby

Order.calculate_all(:price_sum)

# => {price_sum: 123500}

```



If you have a single `group()`, it will return a hash of results with simple keys.



```ruby

Order.group(:department_id).calculate_all(:count_distinct_user_id)

# => {

#   1 => {count_distinct_user_id: 20},

#   2 => {count_distinct_user_id: 10},

#   ...

# }

```



If you have two or more groupings, each result will have an array as a key.



```ruby

Order.group(:department_id).group(:payment_method).calculate_all(:count)

# => {

#   [1, "cash"] => {count: 5},

#   [1, "card"] => {count: 15},

#   [2, "cash"] => {count: 1},

#   ...

# }

```



If you provide only one *string* argument to `#calculate_all`, its calculated value will be returned as-is.

This is just to make grouped companion to `Model.group(...).count` and friends, but for arbitrary expressions

with aggregate functions.



```ruby

Order.group(:payment_method).calculate_all('CAST(SUM(price) AS decimal) / COUNT(DISTINCT user_id)')

# => {

#   "card" => 0.524e3,

#   "cash" => 0.132e3

# }

```



Otherwise, the results will be returned as hash(es) with symbol keys.



```ruby

Order.group(:department_id).group(:payment_method).calculate_all(

  :min_price, type: :payment_method, expr1: 'count(distinct user_id)'

)

# => {

#   [1, 'cash'] => {min_price: 100, type: 'cash', expr1: 5},

#   [1, 'card'] => {min_price: 150, type: 'card', expr1: 15},

#   ...

# }

```



You can pass a block to `calculate_all`. Rows will be passed to it, and returned value will be used instead of

the row in the result hash (or returned as-is if there's no grouping).



```ruby

Order.group(:country_id).calculate_all(:count, :avg_price) { |count:, avg_price:|

  "#{count} orders, #{avg_price.to_i} dollars average"

}

# => {

#   1 => "5 orders, 120 dollars average",

#   2 => "10 orders, 200 dollars average"

# }



Order.group(:country_id).calculate_all("AVG(price)") { |avg_price| avg_price.to_i }

# => {

#   1 => 120,

#   2 => 200

# }



Order.calculate_all(:count, :max_price, &OpenStruct.method(:new))

# => #



Stats = Data.define(:count, :max_price) do

  # needed only for groupdate to provide defaults for empty periods

  def initialize(count: 0, max_price: nil) = super

end

Order.group_by_year(:created_at).calculate_all(*Stats.members, &Stats.method(:new))

# => {

#   Wed, 01 Jan 2014 => #,

#   Thu, 01 Jan 2015 => #,

#   Fri, 01 Jan 2016 => #

# }

```



## groupdate compatibility



calculate-all should work with [groupdate](https://github.com/ankane/groupdate) too:



```ruby

Order.group_by_year(:created_at, last: 5).calculate_all(:price_min, :price_max)

# => {

#   Sun, 01 Jan 2012 => {},

#   Tue, 01 Jan 2013 => {},

#   Wed, 01 Jan 2014 => {},

#   Thu, 01 Jan 2015 => {},

#   Fri, 01 Jan 2016 => {:price_min=>100, :price_max=>500}

# }

```



It works even with groupdate < 4, though you'd have to explicitly provide `default_value: {}` for blank periods.



## Installation



Add this line to your application's Gemfile:



```ruby

gem 'calculate-all'

```



And then execute:



    $ bundle



Or install it yourself as:



    $ gem install calculate-all



## Development



After checking out the repo, run `bin/setup` to install dependencies. Then, run `rake test` to run the tests.

Run `BUNDLE_GEMFILE=gemfiles/activerecord60.gemfile bundle` then `BUNDLE_GEMFILE=gemfiles/activerecord60.gemfile rake`

to test against specific active record version.



To experiment you can load a test database and jump to IRB with



```sh

   rake VERBOSE=1 CONSOLE=1 TESTOPTS="--name=test_console" test:postgresql

```



To install this gem onto your local machine, run `bundle exec rake install`. To release a new version, update the version

number in `version.rb`, and then run `bundle exec rake release`, which will create a git tag for the version, push git commits and tags,

and push the `.gem` file to [rubygems.org](https://rubygems.org).



## Contributing



Bug reports and pull requests are welcome on GitHub at https://github.com/codesnik/calculate-all.



## License



The gem is available as open source under the terms of the [MIT License](http://opensource.org/licenses/MIT).