Remove unused `ActiveRecord::Base.connection_id`

This method appears to have been partially used in connection pool
caching, but it was introduced without much reasoning or any tests. One
edge case test was added later on, but it was focused on implementation
details. This method is no longer used outside of tests, and as such is
removed.

1 files changed, 0 insertions, 12 deletions

diff --git a/activerecord/test/cases/query_cache_test.rb b/activerecord/test/cases/query_cache_test.rb
index d5c01315c1..03ec063671 100644
--- a/activerecord/test/cases/query_cache_test.rb
+++ b/activerecord/test/cases/query_cache_test.rb
@@ -39,18 +39,6 @@ class QueryCacheTest < ActiveRecord::TestCase
     assert ActiveRecord::Base.connection.query_cache_enabled, 'cache on'
   end
 
-  def test_exceptional_middleware_assigns_original_connection_id_on_error
-    connection_id = ActiveRecord::Base.connection_id
-
-    mw = middleware { |env|
-      ActiveRecord::Base.connection_id = self.object_id
-      raise "lol borked"
-    }
-    assert_raises(RuntimeError) { mw.call({}) }
-
-    assert_equal connection_id, ActiveRecord::Base.connection_id
-  end
-
   def test_middleware_delegates
     called = false
     mw = middleware { |env|