Harck

Hacks for ActiveRecord

This library contains hacks for ActiveRecord I have found useful over time. The hacks are not for everyone and should be used with caution. Currently supports Rails 4.2 with Ruby >= 2.0

Add this line to your application's Gemfile:

``` 
# To require all hacks
gem 'harck', :require ['harck/all']

# OR pick and choose your hacks
gem 'harck', :require ['harck/paging_count', 'harck/scub_numeric']
```

Harck::Count - Count + Group queries run as sub-queries

Harck::PagingCount - Count + Group safe count query for paging

Harck::ScrubNumeric - Scrub non-numeric characters before setting numeric data types

Harck::UsDate & Harck::UsDateTime - Try to parse US formatted dates correctly

If you have used the ActiveRecord query method .group with a paging gem you've probably encountered some problems. When used with .group, .count returns a hash. In order for paging to work, you must get the length of the hash to determine your total result set. While the hash "feature" sounds great, if you have a large data set, and setup paging you may discover your app is devouring memory, which is always fun to debug. You may have also had issues with unexpected count results if you had DISTINCT set in your select statement and expected AR to respect it.

The Count hack forces all .count calls on ActiveRecord::Relations with .group values or with distinct select statements to perform a subquery for the dataset which is placed in the FROM statement for the count.

```
2.3.0 :001 > require "harck/count"
 => true

2.3.0 :002 > User.group(:name).count
(0.4ms)  SELECT COUNT(*) FROM (SELECT `users`.`name` FROM `users` GROUP BY `users`.`name`) from_subquery_for_count

2.3.0 :003 > User.select("DISTINCT(name)").count
(0.4ms)  SELECT COUNT(*) FROM (SELECT DISTINCT(name) FROM `users`) from_subquery_for_count

2.3.0 :004 > User.select(:name).distinct.count
(0.4ms)  SELECT COUNT(*) FROM (SELECT DISTINCT(name) FROM `users`) from_subquery_for_count

```

If you find you like this hack but need to perform a COUNT on a GROUP BY you can still achieve your goal by using .pluck('COUNT(foo)')[0]

If you do not want change the default functionality of .count but do want a work around COUNT for paging you can use .paging_count, which will always return an integer. You may have to patch your favorite paging gem but at least your app won't be brought to its knees by a COUNT + GROUP BY query that returns a hash with 2 million items.

```
2.3.0 :001 > require "harck/paging_count"
=> true

2.3.0 :002 > User.group(:name).paging_count
(0.04ms)  SELECT COUNT(*) FROM (SELECT `users`.* FROM `users` GROUP BY `users`.`name`) subquery

```

Does your ActiveRecord model accept money strings for numeric attributes? Does your app have a various ugly filters to remove unwanted characters from numeric strings. ScrubNumeric is the hack for you.

```
2.3.0 :001 > require "harck/scrub_numeric"
=> true

2.3.0 :002 > 2.3.0 :013 > user = User.new(money: "$123.12 ", :clicks => "have 2")
=> #<User id: nil, name: nil, clicks: 2, money: #<BigDecimal:7fee83aab6c0,'0.12312E3',18(27)>> 

2.3.0 :013 > user.money.to_s
=> "123.12" 

```

For me, without fail, one of the first causes for date time inconsistencies when working with outside data sources has been US date format parsing. The Harck::UsDate and Harck::UsDateTime hacks allow ActiveRecord to correctly parse US date formats.

```
2.3.0 :001 > require "harck/us_date"
=> true

2.3.0 :002 > 2.3.0 :013 > user = User.new(date: "02-12-2014")
=> #<User id: nil, name: nil, clicks: 0, money: nil, date = "2014-02-12"> 

2.3.0 :003 > user.date
=> Fri, 12 Feb 2016 

2.3.0 :001 > require "harck/us_date_time"
=> true

2.3.0 :002 > 2.3.0 :013 > user = User.new(datetime: "02-12-2014 02:55 pm")
=> #<User id: nil, name: nil, clicks: 0, money: nil, datetime = "2014-12-02 14:55:00"> 

2.3.0 :007 > user.datetime
=> 2014-12-02 14:55:00 UTC

```

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

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.

Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/harck.

The gem is available as open source under the terms of the MIT License.