Change sqlite3 boolean serialization to use 1 and 0

Abstract boolean serialization has been using 't' and 'f', with MySQL
overriding that to use 1 and 0.

This has the advantage that SQLite natively recognizes 1 and 0 as true
and false, but does not natively recognize 't' and 'f'.

This change in serialization requires a migration of stored boolean data
for SQLite databases, so it's implemented behind a configuration flag
whose default false value is deprecated. The flag itself can be
deprecated in a future version of Rails.  While loaded models will give
the correct result for boolean columns without migrating old data,
where() clauses will interact incorrectly with old data.

While working in this area, also change the abstract adapter to use
`"TRUE"` and `"FALSE"` as quoted values and `true` and `false` for
unquoted.  These are supported by PostreSQL, and MySQL remains
overriden.

4 files changed, 62 insertions, 4 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb b/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
index 61233dcc51..de78c6db44 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
@@ -106,19 +106,19 @@ module ActiveRecord
       end
 
       def quoted_true
-        "'t'".freeze
+        "TRUE".freeze
       end
 
       def unquoted_true
-        "t".freeze
+        true
       end
 
       def quoted_false
-        "'f'".freeze
+        "FALSE".freeze
       end
 
       def unquoted_false
-        "f".freeze
+        false
       end
 
       # Quote date/time values for use in SQL input. Includes microseconds
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3/quoting.rb b/activerecord/lib/active_record/connection_adapters/sqlite3/quoting.rb
index 7276a65098..04dd7fd357 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3/quoting.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3/quoting.rb
@@ -22,6 +22,22 @@ module ActiveRecord
           "x'#{value.hex}'"
         end
 
+        def quoted_true
+          ActiveRecord::ConnectionAdapters::SQLite3Adapter.represent_boolean_as_integer ? "1".freeze : "'t'".freeze
+        end
+
+        def unquoted_true
+          ActiveRecord::ConnectionAdapters::SQLite3Adapter.represent_boolean_as_integer ? 1 : "t".freeze
+        end
+
+        def quoted_false
+          ActiveRecord::ConnectionAdapters::SQLite3Adapter.represent_boolean_as_integer ? "0".freeze : "'f'".freeze
+        end
+
+        def unquoted_false
+          ActiveRecord::ConnectionAdapters::SQLite3Adapter.represent_boolean_as_integer ? 0 : "f".freeze
+        end
+
         private
 
           def _type_cast(value)
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
index 04129841e4..b79dbe0733 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
@@ -72,6 +72,23 @@ module ActiveRecord
         boolean:      { name: "boolean" }
       }
 
+      ##
+      # :singleton-method:
+      # Indicates whether boolean values are stored in sqlite3 databases as 1
+      # and 0 or 't' and 'f'. Leaving `ActiveRecord::ConnectionAdapters::SQLite3Adapter.represent_boolean_as_integer`
+      # set to false is deprecated. SQLite databases have used 't' and 'f' to
+      # serialize boolean values and must have old data converted to 1 and 0
+      # (its native boolean serialization) before setting this flag to true.
+      # Conversion can be accomplished by setting up a rake task which runs
+      #
+      #   ExampleModel.where("boolean_column = 't'").update_all(boolean_column: 1)
+      #   ExampleModel.where("boolean_column = 't'").update_all(boolean_column: 0)
+      # for all models and all boolean columns, after which the flag must be set
+      # to true by adding the following to your application.rb file:
+      #
+      #   ActiveRecord::ConnectionAdapters::SQLite3Adapter.represent_boolean_as_integer = true
+      class_attribute :represent_boolean_as_integer, default: false
+
       class StatementPool < ConnectionAdapters::StatementPool
         private
 
@@ -512,5 +529,6 @@ module ActiveRecord
           execute("PRAGMA foreign_keys = ON", "SCHEMA")
         end
     end
+    ActiveSupport.run_load_hooks(:active_record_sqlite3adapter, SQLite3Adapter)
   end
 end
diff --git a/activerecord/lib/active_record/railtie.rb b/activerecord/lib/active_record/railtie.rb
index 9cca103a18..962ed880b9 100644
--- a/activerecord/lib/active_record/railtie.rb
+++ b/activerecord/lib/active_record/railtie.rb
@@ -174,5 +174,29 @@ end_warning
         end
       end
     end
+
+    initializer "active_record.check_represent_sqlite3_boolean_as_integer" do
+      config.after_initialize do
+        ActiveSupport.on_load(:active_record_sqlite3adapter) do
+          unless ActiveRecord::ConnectionAdapters::SQLite3Adapter.represent_boolean_as_integer
+            ActiveSupport::Deprecation.warn <<-MSG
+Leaving `ActiveRecord::ConnectionAdapters::SQLite3Adapter.represent_boolean_as_integer`
+set to false is deprecated. SQLite databases have used 't' and 'f' to serialize
+boolean values and must have old data converted to 1 and 0 (its native boolean
+serialization) before setting this flag to true. Conversion can be accomplished
+by setting up a rake task which runs
+
+  ExampleModel.where("boolean_column = 't'").update_all(boolean_column: 1)
+  ExampleModel.where("boolean_column = 't'").update_all(boolean_column: 0)
+
+for all models and all boolean columns, after which the flag must be set to
+true by adding the following to your application.rb file:
+
+  ActiveRecord::ConnectionAdapters::SQLite3Adapter.represent_boolean_as_integer = true
+MSG
+          end
+        end
+      end
+    end
   end
 end