aboutsummaryrefslogtreecommitdiffstats
path: root/activerecord/lib/active_record/relation/merger.rb
blob: 545bf5debc0432fdff16e2e49c179d083865490f (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
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
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
require 'active_support/core_ext/hash/keys'
require "set"

module ActiveRecord
  class Relation
    class HashMerger # :nodoc:
      attr_reader :relation, :hash

      def initialize(relation, hash)
        hash.assert_valid_keys(*Relation::VALUE_METHODS)

        @relation = relation
        @hash     = hash
      end

      def merge #:nodoc:
        Merger.new(relation, other).merge
      end

      # Applying values to a relation has some side effects. E.g.
      # interpolation might take place for where values. So we should
      # build a relation to merge in rather than directly merging
      # the values.
      def other
        other = Relation.create(relation.klass, relation.table)
        hash.each { |k, v|
          if k == :joins
            if Hash === v
              other.joins!(v)
            else
              other.joins!(*v)
            end
          elsif k == :select
            other._select!(v)
          else
            other.send("#{k}!", v)
          end
        }
        other
      end
    end

    class Merger # :nodoc:
      attr_reader :relation, :values, :other

      def initialize(relation, other)
        @relation = relation
        @values   = other.values
        @other    = other
      end

      NORMAL_VALUES = Relation::SINGLE_VALUE_METHODS +
                      Relation::MULTI_VALUE_METHODS -
                      [:joins, :where, :order, :bind, :reverse_order, :lock, :create_with, :reordering, :from] # :nodoc:

      def normal_values
        NORMAL_VALUES
      end

      def merge
        normal_values.each do |name|
          value = values[name]
          # The unless clause is here mostly for performance reasons (since the `send` call might be moderately
          # expensive), most of the time the value is going to be `nil` or `.blank?`, the only catch is that
          # `false.blank?` returns `true`, so there needs to be an extra check so that explicit `false` values
          # don't fall through the cracks.
          unless value.nil? || (value.blank? && false != value)
            if name == :select
              relation._select!(*value)
            else
              relation.send("#{name}!", *value)
            end
          end
        end

        merge_multi_values
        merge_single_values
        merge_joins

        relation
      end

      private

      def merge_joins
        return if values[:joins].blank?

        if other.klass == relation.klass
          relation.joins!(*values[:joins])
        else
          joins_dependency, rest = values[:joins].partition do |join|
            case join
            when Hash, Symbol, Array
              true
            else
              false
            end
          end

          join_dependency = ActiveRecord::Associations::JoinDependency.new(other.klass,
                                                                           joins_dependency,
                                                                           [])
          relation.joins! rest

          @relation = relation.joins join_dependency
        end
      end

      def merge_multi_values
        lhs_wheres = relation.where_values
        rhs_wheres = values[:where] || []

        lhs_binds  = relation.bind_values
        rhs_binds  = values[:bind] || []

        removed, kept = partition_overwrites(lhs_wheres, rhs_wheres)

        where_values = kept + rhs_wheres
        bind_values  = filter_binds(lhs_binds, removed) + rhs_binds

        conn = relation.klass.connection
        bv_index = 0
        where_values.map! do |node|
          if Arel::Nodes::Equality === node && Arel::Nodes::BindParam === node.right
            substitute = conn.substitute_at(bind_values[bv_index].first, bv_index)
            bv_index += 1
            Arel::Nodes::Equality.new(node.left, substitute)
          else
            node
          end
        end

        relation.where_values = where_values
        relation.bind_values  = bind_values

        if values[:reordering]
          # override any order specified in the original relation
          relation.reorder! values[:order]
        elsif values[:order]
          # merge in order_values from relation
          relation.order! values[:order]
        end

        relation.extend(*values[:extending]) unless values[:extending].blank?
      end

      def merge_single_values
        relation.from_value          = values[:from] unless relation.from_value
        relation.lock_value          = values[:lock] unless relation.lock_value

        unless values[:create_with].blank?
          relation.create_with_value = (relation.create_with_value || {}).merge(values[:create_with])
        end
      end

      def filter_binds(lhs_binds, removed_wheres)
        return lhs_binds if removed_wheres.empty?

        set = Set.new removed_wheres.map { |x| x.left.name.to_s }
        lhs_binds.dup.delete_if { |col,_| set.include? col.name }
      end

      # Remove equalities from the existing relation with a LHS which is
      # present in the relation being merged in.
      # returns [things_to_remove, things_to_keep]
      def partition_overwrites(lhs_wheres, rhs_wheres)
        if lhs_wheres.empty? || rhs_wheres.empty?
          return [[], lhs_wheres]
        end

        nodes = rhs_wheres.find_all do |w|
          w.respond_to?(:operator) && w.operator == :==
        end
        seen = Set.new(nodes) { |node| node.left }

        lhs_wheres.partition do |w|
          w.respond_to?(:operator) && w.operator == :== && seen.include?(w.left)
        end
      end
    end
  end
end