Introduction to DataMiner

DataMiner is an ActiveRecord plugin which simplifies creating complex data-probing queries using a familiar, rails-like syntax.

results = Nimrod.mine do
  sum :price
  count :all
end

This would result in the following query being executed:

SELECT SUM(price) as sum_price, COUNT(*) as count_all FROM nimrods;

If the query only has one result, the mine function returns a Hash with a set of pairs, one for each field in the query. The above example would return the following, given 54 rows each with a price of 9.95:

{ :sum_price => 537.5, :count => 54 }

Function calls are captured using method_missing, so any functions present in your chosen database system may be used:

results = Nimrod.mind do
  stddev :price
  avg :length
  fictional_function :year
end

DataMiner will also accept a :group key in its arguments. It will pass the value of :group as the GROUP BY clause in the query. The field(s) included in the group parameter are automatically included in the result set:

results = Nimrod.mine(:group => "year") do
  sum :price
  count :all
end

=> [{ :year => 2005, :sum_price => 537.5, :count => 54 }, { :year => 2007, :sum_price => 134.55, :count => 352 }]

If the query results in more than one row, an Array containing the corresponding Hash for each row is returned.

Because mine uses the find method of ActiveRecord::Base to query the database, any options that can be passed to find can be passed to mine:

results = Nimrod.mine(:conditions => ["length > ?", 50], :group => "year, length") do
  sum :price
  count :all
end

Function Arguments

DataMiner currently supports two arguments that can be passed to each function call: :as and :after

:as allows you to override the default naming convention of each result field:

results = Nimrod.mine do
  sum :price, :as => "total_price_in_set"
end

# => SELECT SUM(price) as total_price_in_set, COUNT(*) as count_all FROM nimrods;

By default, DataMiner will attempt to convert strings to numeric using to_f. To override this functionality, pass a block to :after:

results = Nimrod.mine do
  sum :price, :as => "total_price_in_cents", :after => lambda { |x| x.to_f * 100 }
end

Legals

Copyright (c) 2009 Daniel Cheail, released under the MIT license