1 files changed, 168 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/result.rb b/activerecord/lib/active_record/result.rb
new file mode 100644
index 0000000000..da6d10b6ec
--- /dev/null
+++ b/activerecord/lib/active_record/result.rb
@@ -0,0 +1,168 @@
+# frozen_string_literal: true
+
+module ActiveRecord
+  ###
+  # This class encapsulates a result returned from calling
+  # {#exec_query}[rdoc-ref:ConnectionAdapters::DatabaseStatements#exec_query]
+  # on any database connection adapter. For example:
+  #
+  #   result = ActiveRecord::Base.connection.exec_query('SELECT id, title, body FROM posts')
+  #   result # => #<ActiveRecord::Result:0xdeadbeef>
+  #
+  #   # Get the column names of the result:
+  #   result.columns
+  #   # => ["id", "title", "body"]
+  #
+  #   # Get the record values of the result:
+  #   result.rows
+  #   # => [[1, "title_1", "body_1"],
+  #         [2, "title_2", "body_2"],
+  #         ...
+  #        ]
+  #
+  #   # Get an array of hashes representing the result (column => value):
+  #   result.to_a
+  #   # => [{"id" => 1, "title" => "title_1", "body" => "body_1"},
+  #         {"id" => 2, "title" => "title_2", "body" => "body_2"},
+  #         ...
+  #        ]
+  #
+  #   # ActiveRecord::Result also includes Enumerable.
+  #   result.each do |row|
+  #     puts row['title'] + " " + row['body']
+  #   end
+  class Result
+    include Enumerable
+
+    attr_reader :columns, :rows, :column_types
+
+    def initialize(columns, rows, column_types = {})
+      @columns      = columns
+      @rows         = rows
+      @hash_rows    = nil
+      @column_types = column_types
+    end
+
+    # Returns true if this result set includes the column named +name+
+    def includes_column?(name)
+      @columns.include? name
+    end
+
+    # Returns the number of elements in the rows array.
+    def length
+      @rows.length
+    end
+
+    # Calls the given block once for each element in row collection, passing
+    # row as parameter.
+    #
+    # Returns an +Enumerator+ if no block is given.
+    def each
+      if block_given?
+        hash_rows.each { |row| yield row }
+      else
+        hash_rows.to_enum { @rows.size }
+      end
+    end
+
+    def to_hash
+      ActiveSupport::Deprecation.warn(<<-MSG.squish)
+        `ActiveRecord::Result#to_hash` has been renamed to `to_a`.
+        `to_hash` is deprecated and will be removed in Rails 6.1.
+      MSG
+      to_a
+    end
+
+    alias :map! :map
+    alias :collect! :map
+
+    # Returns true if there are no records, otherwise false.
+    def empty?
+      rows.empty?
+    end
+
+    # Returns an array of hashes representing each row record.
+    def to_ary
+      hash_rows
+    end
+
+    alias :to_a :to_ary
+
+    def [](idx)
+      hash_rows[idx]
+    end
+
+    # Returns the first record from the rows collection.
+    # If the rows collection is empty, returns +nil+.
+    def first
+      return nil if @rows.empty?
+      Hash[@columns.zip(@rows.first)]
+    end
+
+    # Returns the last record from the rows collection.
+    # If the rows collection is empty, returns +nil+.
+    def last
+      return nil if @rows.empty?
+      Hash[@columns.zip(@rows.last)]
+    end
+
+    def cast_values(type_overrides = {}) # :nodoc:
+      if columns.one?
+        # Separated to avoid allocating an array per row
+
+        type = column_type(columns.first, type_overrides)
+
+        rows.map do |(value)|
+          type.deserialize(value)
+        end
+      else
+        types = columns.map { |name| column_type(name, type_overrides) }
+
+        rows.map do |values|
+          Array.new(values.size) { |i| types[i].deserialize(values[i]) }
+        end
+      end
+    end
+
+    def initialize_copy(other)
+      @columns      = columns.dup
+      @rows         = rows.dup
+      @column_types = column_types.dup
+      @hash_rows    = nil
+    end
+
+    private
+
+      def column_type(name, type_overrides = {})
+        type_overrides.fetch(name) do
+          column_types.fetch(name, Type.default_value)
+        end
+      end
+
+      def hash_rows
+        @hash_rows ||=
+          begin
+            # We freeze the strings to prevent them getting duped when
+            # used as keys in ActiveRecord::Base's @attributes hash
+            columns = @columns.map(&:-@)
+            length  = columns.length
+
+            @rows.map { |row|
+              # In the past we used Hash[columns.zip(row)]
+              #  though elegant, the verbose way is much more efficient
+              #  both time and memory wise cause it avoids a big array allocation
+              #  this method is called a lot and needs to be micro optimised
+              hash = {}
+
+              index = 0
+              while index < length
+                hash[columns[index]] = row[index]
+                index += 1
+              end
+
+              hash
+            }
+          end
+      end
+  end
+end