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 



4
5
6
7
8
 
# 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 



41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
 
# File 'lib/switchman/active_record/calculations.rb', line 41

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_for(column_name), "average")
      r["count"] = type_cast_calculated_value(r["count"], column_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_for(column_name), "average")
  end
  result
end

#execute_grouped_calculation(operation, column_name, distinct) ⇒ Object

See activerecord#execute_grouped_calculation



62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
 
# File 'lib/switchman/active_record/calculations.rb', line 62

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_for(opts[:column_name]), opts[:operation])
      row['count'] = row['count'].to_i if opts[:operation] == 'average'

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



21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
 
# File 'lib/switchman/active_record/calculations.rb', line 21

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_name) ⇒ Object 



10
11
12
13
14
15
16
17
18
19
 
# 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