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_simple_average(column_name, distinct) ⇒ Object 



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# File 'lib/switchman/active_record/calculations.rb', line 55

def calculate_simple_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"], column_or_type_for(column_name), "average")
      r["count"] = type_cast_calculated_value(r["count"], column_or_type_for(column_name), "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.first["average"], column_or_type_for(column_name), "average")
  end
  result
end

#execute_grouped_calculation(operation, column_name, distinct) ⇒ Object

See activerecord#execute_grouped_calculation



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# File 'lib/switchman/active_record/calculations.rb', line 76

def execute_grouped_calculation(operation, column_name, distinct)
  opts = grouped_calculation_options(operation.to_s.downcase, column_name, distinct)

  relation = build_grouped_calculation_relation(opts)
  target_shard = Shard.current(:default)

  rows = relation.activate do |rel, shard|
    calculated_data = klass.connection.select_all(rel)

    if opts[:association]
      key_ids     = calculated_data.collect { |row| row[opts[:group_aliases].first] }
      key_records = opts[:association].klass.base_class.where(:id => key_ids)
      key_records = Hash[key_records.map { |r| [Shard.relative_id_for(r, shard, target_shard), r] }]
    end

    calculated_data.map do |row|
      row[opts[:aggregate_alias]] = type_cast_calculated_value(
          row[opts[:aggregate_alias]], column_or_type_for(opts[:column_name]), opts[:operation])
      row['count'] = row['count'].to_i if opts[:operation] == 'average'

      opts[:group_columns].each do |aliaz, column_or_type, column_name|
        if opts[:associated] && (aliaz == opts[:group_aliases].first)
          row[aliaz] = key_records[Shard.relative_id_for(row[aliaz], shard, target_shard)]
        elsif column_name && @klass.sharded_column?(column_name)
          row[aliaz] = Shard.relative_id_for(type_cast_calculated_value(row[aliaz], column_or_type), shard, target_shard)
        end
      end
      row
    end
  end

  compact_grouped_calculation_rows(rows, opts)
end

#execute_simple_calculation_with_sharding(operation, column_name, distinct) ⇒ Object 



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# File 'lib/switchman/active_record/calculations.rb', line 35

def execute_simple_calculation_with_sharding(operation, column_name, distinct)
  operation = operation.to_s.downcase
  if operation == "average"
    result = calculate_simple_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_names) ⇒ Object 



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

def pluck_with_sharding(*column_names)
  target_shard = Shard.current(klass.shard_category)
  shard_count = 0
  result = self.activate do |relation, shard|
    shard_count += 1
    results = relation.pluck_without_sharding(*column_names)
    if column_names.length > 1
      column_names.each_with_index do |column_name, idx|
        if klass.sharded_column?(column_name)
          results.each{|result| result[idx] = Shard.relative_id_for(result[idx], shard, target_shard)}
        end
      end
    else
      if klass.sharded_column?(column_names.first.to_s)
        results = results.map{|result| Shard.relative_id_for(result, shard, target_shard)}
      end
    end
    results
  end
  if uniq_value && shard_count > 1
    result.uniq!
  end
  result
end