Perf: micro optimised Result column hash_row creation

1 files changed, 15 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/result.rb b/activerecord/lib/active_record/result.rb
index 253368ae5b..d0f1cb5b75 100644
--- a/activerecord/lib/active_record/result.rb
+++ b/activerecord/lib/active_record/result.rb
@@ -93,7 +93,21 @@ module ActiveRecord
           # used as keys in ActiveRecord::Base's @attributes hash
           columns = @columns.map { |c| c.dup.freeze }
           @rows.map { |row|
-            Hash[columns.zip(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
+            length = columns.length
+
+            while index < length
+              hash[columns[index]] = row[index]
+              index += 1
+            end
+
+            hash
           }
         end
     end