Module: Switchman::ActiveRecord::Calculations

Defined in:
lib/switchman/active_record/calculations.rb

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.included(klass) ⇒ Object 



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# File 'lib/switchman/active_record/calculations.rb', line 4

def self.included(klass)
  %w{execute_simple_calculation pluck}.each do |method|
    klass.alias_method_chain(method, :sharding)
  end
end

Instance Method Details

#calculate_average(column_name, distinct) ⇒ Object 



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# File 'lib/switchman/active_record/calculations.rb', line 42

def calculate_average(column_name, distinct)
  # See activerecord#execute_simple_calculation
  relation = reorder(nil)
  column = aggregate_column(column_name)
  relation.select_values = [operation_over_aggregate_column(column, "average", distinct).as("average"),
                            operation_over_aggregate_column(column, "count", distinct).as("count")]

  initial_results = relation.activate{ |rel| @klass.connection.select_all(rel) }
  if initial_results.is_a?(Array)
    initial_results.each do |r|
      r["average"] = type_cast_calculated_value(r["average"], nil, "average")
      r["count"] = type_cast_calculated_value(r["count"], nil, "count")
    end
    result = initial_results.map{|r| r["average"] * r["count"]}.sum / initial_results.map{|r| r["count"]}.sum
  else
    result = type_cast_calculated_value(initial_results["average"], nil, "average")
  end
  result
end

#execute_simple_calculation_with_sharding(operation, column_name, distinct) ⇒ Object

TODO: grouped calculations



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# File 'lib/switchman/active_record/calculations.rb', line 22

def execute_simple_calculation_with_sharding(operation, column_name, distinct)
  operation = operation.to_s.downcase
  if operation == "average"
    result = calculate_average(column_name, distinct)
  else
    result = self.activate{ |relation| relation.send(:execute_simple_calculation_without_sharding, operation, column_name, distinct) }
    if result.is_a?(Array)
      case operation
      when "count", "sum"
        result = result.sum
      when "minimum"
        result = result.min
      when "maximum"
        result = result.max
      end
    end
  end
  result
end

#pluck_with_sharding(column_name) ⇒ Object 



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# File 'lib/switchman/active_record/calculations.rb', line 10

def pluck_with_sharding(column_name)
  target_shard = Shard.current(klass.shard_category)
  self.activate do |relation, shard|
    results = relation.pluck_without_sharding(column_name)
    if klass.sharded_column?(column_name.to_s)
      results = results.map{|result| Shard.relative_id_for(result, shard, target_shard)}
    end
    results
  end
end