pg, map `char` and `name` types as string. [dark-panda & Yves Senn]

Closes #10802.

activerecord/CHANGELOG.md

+*   Handle `name` and `"char"` column types in the PostgreSQL adapter.
+
+    `name` and `"char"` are special character types used internally by
+    PostgreSQL and are used by internal system catalogs. These field types
+    can sometimes show up in structure-sniffing queries that feature internal system
+    structures or with certain PostgreSQL extensions.
+
+    *J Smith*, *Yves Senn*
+
 *   Fix `PostgreSQLAdapter::OID::Float#type_cast` to convert Infinity and
     NaN PostgreSQL values into a native Ruby `Float::INFINITY` and `Float::NAN`
 

activerecord/lib/active_record/connection_adapters/postgresql/oid.rb

@@ -409,6 +409,7 @@ def self.registered_type?(name)
         register_type 'text', OID::Text.new
         register_type 'varchar', OID::String.new
         alias_type 'char', 'varchar'
+        alias_type 'name', 'varchar'
         alias_type 'bpchar', 'varchar'
         register_type 'bool', OID::Boolean.new
         register_type 'bit', OID::Bit.new

activerecord/test/cases/adapters/postgresql/datatype_test.rb

 require "cases/helper"
+require 'support/ddl_helper'
 
 class PostgresqlArray < ActiveRecord::Base
 end
@@ -315,3 +316,25 @@ def test_timestamp_with_zone_values_without_rails_time_zone_support
     @connection.reconnect!
   end
 end
+
+class PostgresqlInternalDataTypeTest < ActiveRecord::TestCase
+  include DdlHelper
+
+  setup do
+    @connection = ActiveRecord::Base.connection
+  end
+
+  def test_name_column_type
+    with_example_table @connection, 'ex', 'data name' do
+      column = @connection.columns('ex').find { |col| col.name == 'data' }
+      assert_equal :string, column.type
+    end
+  end
+
+  def test_char_column_type
+    with_example_table @connection, 'ex', 'data "char"' do
+      column = @connection.columns('ex').find { |col| col.name == 'data' }
+      assert_equal :string, column.type
+    end
+  end
+end