Use frozen-string-literal in ActiveRecord

69 files changed, 138 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb b/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
index 627b753f01..c11b7b012f 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "thread"
 require "concurrent/map"
 require "monitor"
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/database_limits.rb b/activerecord/lib/active_record/connection_adapters/abstract/database_limits.rb
index 407e019326..7a9e7add24 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/database_limits.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/database_limits.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters # :nodoc:
     module DatabaseLimits
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
index 879626b72a..f2715cdab0 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters # :nodoc:
     module DatabaseStatements
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/query_cache.rb b/activerecord/lib/active_record/connection_adapters/abstract/query_cache.rb
index c352ddfc11..077e8beba9 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/query_cache.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/query_cache.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters # :nodoc:
     module QueryCache
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb b/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
index de78c6db44..b637518fc8 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/core_ext/big_decimal/conversions"
 require "active_support/multibyte/chars"
 
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/savepoints.rb b/activerecord/lib/active_record/connection_adapters/abstract/savepoints.rb
index 3a06f75292..52a796b926 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/savepoints.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/savepoints.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module Savepoints
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb
index 8865e7c703..8bf3879a4c 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/core_ext/string/strip"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
index a30fbe0e05..3b2c51ef94 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters #:nodoc:
     # Abstract representation of an index definition on a table. Instances of
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_dumper.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_dumper.rb
index 34036d8a1d..9be26254b2 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_dumper.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_dumper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters # :nodoc:
     # The goal of this module is to move Adapter specific column
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
index 475463c4fd..989ebc81a9 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "../../migration/join_table"
 require "active_support/core_ext/string/access"
 require "digest"
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb b/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb
index f63d09039f..147e16e9fa 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     class TransactionState
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index 30b29e7007..ed9caee0aa 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "../type"
 require_relative "determine_if_preparable_visitor"
 require_relative "schema_cache"
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
index 06976aa769..d97d3af2a6 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "abstract_adapter"
 require_relative "statement_pool"
 require_relative "mysql/column"
diff --git a/activerecord/lib/active_record/connection_adapters/column.rb b/activerecord/lib/active_record/connection_adapters/column.rb
index 61cd7ae4cc..16273fb5f1 100644
--- a/activerecord/lib/active_record/connection_adapters/column.rb
+++ b/activerecord/lib/active_record/connection_adapters/column.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # :stopdoc:
   module ConnectionAdapters
diff --git a/activerecord/lib/active_record/connection_adapters/connection_specification.rb b/activerecord/lib/active_record/connection_adapters/connection_specification.rb
index 3e4ea28f63..29542f917e 100644
--- a/activerecord/lib/active_record/connection_adapters/connection_specification.rb
+++ b/activerecord/lib/active_record/connection_adapters/connection_specification.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "uri"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/connection_adapters/determine_if_preparable_visitor.rb b/activerecord/lib/active_record/connection_adapters/determine_if_preparable_visitor.rb
index 0fdc185c45..3dcb916d99 100644
--- a/activerecord/lib/active_record/connection_adapters/determine_if_preparable_visitor.rb
+++ b/activerecord/lib/active_record/connection_adapters/determine_if_preparable_visitor.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module DetermineIfPreparableVisitor
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/column.rb b/activerecord/lib/active_record/connection_adapters/mysql/column.rb
index c9ad47c035..fa1541019d 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/column.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/column.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module MySQL
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/database_statements.rb b/activerecord/lib/active_record/connection_adapters/mysql/database_statements.rb
index bda482a00f..00b56ee9ae 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/database_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/database_statements.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module MySQL
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/explain_pretty_printer.rb b/activerecord/lib/active_record/connection_adapters/mysql/explain_pretty_printer.rb
index 9691060cd3..20c3c83664 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/explain_pretty_printer.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/explain_pretty_printer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module MySQL
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/quoting.rb b/activerecord/lib/active_record/connection_adapters/mysql/quoting.rb
index 4441c1e2f8..803babf55d 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/quoting.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/quoting.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module MySQL
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/schema_creation.rb b/activerecord/lib/active_record/connection_adapters/mysql/schema_creation.rb
index eea4984680..5a35823c72 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/schema_creation.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/schema_creation.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module MySQL
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/schema_definitions.rb b/activerecord/lib/active_record/connection_adapters/mysql/schema_definitions.rb
index 6d88c14d50..b22a2e4da7 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/schema_definitions.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module MySQL
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb b/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb
index a46d9f8cbb..fbe3596dda 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/schema_dumper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module MySQL
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb
index 24f8ff6367..1d87d60ba9 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module MySQL
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/type_metadata.rb b/activerecord/lib/active_record/connection_adapters/mysql/type_metadata.rb
index 9ad6a6c0d0..7ad0944d51 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/type_metadata.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/type_metadata.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module MySQL
diff --git a/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb b/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
index c5c0a071e7..2c2321872d 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "abstract_mysql_adapter"
 require_relative "mysql/database_statements"
 
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/column.rb b/activerecord/lib/active_record/connection_adapters/postgresql/column.rb
index 3ad1911a28..1b67cee24b 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/column.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/column.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     # PostgreSQL-specific extensions to column definitions in a table.
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb b/activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb
index ebf1715ed0..8db2a645af 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/explain_pretty_printer.rb b/activerecord/lib/active_record/connection_adapters/postgresql/explain_pretty_printer.rb
index 99f3a5bbdf..086a5dcc15 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/explain_pretty_printer.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/explain_pretty_printer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb
index 6666622c08..b28418d74f 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "oid/array"
 require_relative "oid/bit"
 require_relative "oid/bit_varying"
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/array.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/array.rb
index a73a8c1726..d6852082ac 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/array.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/array.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/bit.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/bit.rb
index 0a505f46a7..587e95d192 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/bit.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/bit.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/bit_varying.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/bit_varying.rb
index 4c21097d48..dc7079dda2 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/bit_varying.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/bit_varying.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/bytea.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/bytea.rb
index 702fa8175c..a3c60ecef6 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/bytea.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/bytea.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/cidr.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/cidr.rb
index 5225609e37..66e99d9404 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/cidr.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/cidr.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "ipaddr"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/date_time.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/date_time.rb
index b7acbf7178..cd667422f5 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/date_time.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/date_time.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/decimal.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/decimal.rb
index 43d22c8daf..879dba7afd 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/decimal.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/decimal.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/enum.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/enum.rb
index 950d23d516..f70f09ad95 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/enum.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/enum.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/hstore.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/hstore.rb
index 49dd4fc73f..aabe83b85d 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/hstore.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/hstore.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/inet.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/inet.rb
index 96486fa65b..55be71fd26 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/inet.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/inet.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/jsonb.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/jsonb.rb
index a1fec289d4..e0216f1089 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/jsonb.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/jsonb.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/legacy_point.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/legacy_point.rb
index 775eecaf85..7b057a8452 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/legacy_point.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/legacy_point.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/oid.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/oid.rb
index 9c2ac08b30..d8c044320d 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/oid.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/oid.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/point.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/point.rb
index 7c764e7287..02a9c506f6 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/point.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/point.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   Point = Struct.new(:x, :y)
 
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/range.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/range.rb
index 54d5d0902e..7d5d7d91e6 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/range.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/range.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/specialized_string.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/specialized_string.rb
index 564e82a4ac..4ad1344f05 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/specialized_string.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/specialized_string.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/type_map_initializer.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/type_map_initializer.rb
index d9ae1aa7a2..15ae241d50 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/type_map_initializer.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/type_map_initializer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/uuid.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/uuid.rb
index db92333ef7..bc9b8dbfcf 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/uuid.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/uuid.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/vector.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/vector.rb
index b26e876b54..88ef626a16 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/vector.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/vector.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/xml.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/xml.rb
index d40d837cee..042f32fdc3 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/xml.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/xml.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb b/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb
index ee4230c6f2..fc458d0c73 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/referential_integrity.rb b/activerecord/lib/active_record/connection_adapters/postgresql/referential_integrity.rb
index 44a7338bf5..386d22a9bd 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/referential_integrity.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/referential_integrity.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/schema_creation.rb b/activerecord/lib/active_record/connection_adapters/postgresql/schema_creation.rb
index e1d5089115..59f661da25 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_creation.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_creation.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/schema_definitions.rb b/activerecord/lib/active_record/connection_adapters/postgresql/schema_definitions.rb
index 11ea1e5144..f1489e4d69 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_definitions.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/schema_dumper.rb b/activerecord/lib/active_record/connection_adapters/postgresql/schema_dumper.rb
index 5555a46b6b..12c6603081 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_dumper.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_dumper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
index a710ea6cc9..32b01b4a31 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/core_ext/string/strip"
 
 module ActiveRecord
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/type_metadata.rb b/activerecord/lib/active_record/connection_adapters/postgresql/type_metadata.rb
index f57179ae59..b252a76caa 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/type_metadata.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/type_metadata.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     class PostgreSQLTypeMetadata < DelegateClass(SqlTypeMetadata)
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/utils.rb b/activerecord/lib/active_record/connection_adapters/postgresql/utils.rb
index aa7940188a..bfd300723d 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/utils.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/utils.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 66c61b5f4a..b8c2cabb48 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Make sure we're using pg high enough for type casts and Ruby 2.2+ compatibility
 gem "pg", "~> 0.18"
 require "pg"
diff --git a/activerecord/lib/active_record/connection_adapters/schema_cache.rb b/activerecord/lib/active_record/connection_adapters/schema_cache.rb
index 4d339b0a8c..f34b6733da 100644
--- a/activerecord/lib/active_record/connection_adapters/schema_cache.rb
+++ b/activerecord/lib/active_record/connection_adapters/schema_cache.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     class SchemaCache
diff --git a/activerecord/lib/active_record/connection_adapters/sql_type_metadata.rb b/activerecord/lib/active_record/connection_adapters/sql_type_metadata.rb
index 9e12ae0de8..8489bcbf1d 100644
--- a/activerecord/lib/active_record/connection_adapters/sql_type_metadata.rb
+++ b/activerecord/lib/active_record/connection_adapters/sql_type_metadata.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   # :stopdoc:
   module ConnectionAdapters
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3/explain_pretty_printer.rb b/activerecord/lib/active_record/connection_adapters/sqlite3/explain_pretty_printer.rb
index 6fe3e1211e..832fdfe5c4 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3/explain_pretty_printer.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3/explain_pretty_printer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module SQLite3
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3/quoting.rb b/activerecord/lib/active_record/connection_adapters/sqlite3/quoting.rb
index 04dd7fd357..8042dbfea2 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3/quoting.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3/quoting.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module SQLite3
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_creation.rb b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_creation.rb
index bc798d1dbb..b842561317 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_creation.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_creation.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module SQLite3
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_definitions.rb b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_definitions.rb
index e157e4b218..501f17dbad 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_definitions.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module SQLite3
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_dumper.rb b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_dumper.rb
index eec018eda3..ab057c73f1 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_dumper.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_dumper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module SQLite3
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_statements.rb
index 31e83f9260..c155e7f1ac 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3/schema_statements.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module SQLite3
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
index 2fede7b847..10e80179ac 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "abstract_adapter"
 require_relative "statement_pool"
 require_relative "sqlite3/explain_pretty_printer"
diff --git a/activerecord/lib/active_record/connection_adapters/statement_pool.rb b/activerecord/lib/active_record/connection_adapters/statement_pool.rb
index 790db56185..46bd831da7 100644
--- a/activerecord/lib/active_record/connection_adapters/statement_pool.rb
+++ b/activerecord/lib/active_record/connection_adapters/statement_pool.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     class StatementPool # :nodoc: