Avoid creating temporary arrays in ActiveRecord::Result#cast_values in order to speed up pluck

1 files changed, 14 insertions, 5 deletions

diff --git a/activerecord/lib/active_record/result.rb b/activerecord/lib/active_record/result.rb
index 11626c8e31..ffef229be2 100644
--- a/activerecord/lib/active_record/result.rb
+++ b/activerecord/lib/active_record/result.rb
@@ -97,12 +97,21 @@ module ActiveRecord
     end
 
     def cast_values(type_overrides = {}) # :nodoc:
-      types = columns.map { |name| column_type(name, type_overrides) }
-      result = rows.map do |values|
-        types.zip(values).map { |type, value| type.deserialize(value) }
-      end
+      if columns.one?
+        # Separated to avoid allocating an array per row
+
+        type = column_type(columns.first, type_overrides)
 
-      columns.one? ? result.map!(&:first) : result
+        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)