Prefer string patterns for gsub

https://github.com/ruby/ruby/pull/579 - there is a new optimization
since ruby 2.2

Previously regexp patterns were faster (since a string was converted to
regexp underneath anyway). But now string patterns are faster and
better reflect the purpose.

  Benchmark.ips do |bm|
    bm.report('regexp') { 'this is ::a random string'.gsub(/::/, '/') }
    bm.report('string') { 'this is ::a random string'.gsub('::', '/') }
    bm.compare!
  end
  # string: 753724.4 i/s
  # regexp: 501443.1 i/s - 1.50x slower

2 files changed, 2 insertions, 2 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb b/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
index d2840b9498..c228b39c26 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
@@ -77,7 +77,7 @@ module ActiveRecord
       # Quotes a string, escaping any ' (single quote) and \ (backslash)
       # characters.
       def quote_string(s)
-        s.gsub(/\\/, '\&\&').gsub(/'/, "''") # ' (for ruby-mode)
+        s.gsub('\\', '\&\&').gsub("'", "''") # ' (for ruby-mode)
       end
 
       # Quotes the column name. Defaults to no quoting.
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 00fc69c878..ebced66cb1 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -568,7 +568,7 @@ module ActiveRecord
           case default
             # Quoted types
             when /\A[\(B]?'(.*)'::/m
-              $1.gsub(/''/, "'")
+              $1.gsub("''", "'")
             # Boolean types
             when 'true', 'false'
               default