diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 6d01bc67cea82c7a62bba36cae7717d574e5687f..72410ab4963b8d76060c025c446d799618143a71 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,9 @@
+*   Remove deprecated access to connection specification using a string acessor.
+
+    Now all strings will be handled as a URL.
+
+    *Rafael Mendonça França*
+
 *   Change the default `null` value for `timestamps` to `false`.
 
     *Rafael Mendonça França*
diff --git a/activerecord/lib/active_record/connection_adapters/connection_specification.rb b/activerecord/lib/active_record/connection_adapters/connection_specification.rb
index e54e3199ff35581ac90b7547dfbf4ef0a9c8c805..08d46fca96393498871465702155eb2d6d54152c 100644
--- a/activerecord/lib/active_record/connection_adapters/connection_specification.rb
+++ b/activerecord/lib/active_record/connection_adapters/connection_specification.rb
@@ -1,5 +1,4 @@
 require 'uri'
-require 'active_support/core_ext/string/filters'
 
 module ActiveRecord
   module ConnectionAdapters
@@ -210,30 +209,12 @@ def resolve_connection(spec)
           when Symbol
             resolve_symbol_connection spec
           when String
-            resolve_string_connection spec
+            resolve_url_connection spec
           when Hash
             resolve_hash_connection spec
           end
         end
 
-        def resolve_string_connection(spec)
-          # Rails has historically accepted a string to mean either
-          # an environment key or a URL spec, so we have deprecated
-          # this ambiguous behaviour and in the future this function
-          # can be removed in favor of resolve_url_connection.
-          if configurations.key?(spec) || spec !~ /:/
-            ActiveSupport::Deprecation.warn(<<-MSG.squish)
-              Passing a string to ActiveRecord::Base.establish_connection for a
-              configuration lookup is deprecated, please pass a symbol
-              (#{spec.to_sym.inspect}) instead.
-            MSG
-
-            resolve_symbol_connection(spec)
-          else
-            resolve_url_connection(spec)
-          end
-        end
-
         # Takes the environment such as +:production+ or +:development+.
         # This requires that the @configurations was initialized with a key that
         # matches.
diff --git a/activerecord/test/cases/connection_adapters/merge_and_resolve_default_url_config_test.rb b/activerecord/test/cases/connection_adapters/merge_and_resolve_default_url_config_test.rb
index 37ad469476c84585cfc9a5b7cacb57439db0d9d2..9ee92a3cd278923908e8a3619d37ae1a5102c81d 100644
--- a/activerecord/test/cases/connection_adapters/merge_and_resolve_default_url_config_test.rb
+++ b/activerecord/test/cases/connection_adapters/merge_and_resolve_default_url_config_test.rb
@@ -51,34 +51,6 @@ def test_resolver_with_database_uri_and_current_env_symbol_key_and_rack_env
         assert_equal expected, actual
       end
 
-      def test_resolver_with_database_uri_and_and_current_env_string_key
-        ENV['DATABASE_URL'] = "postgres://localhost/foo"
-        config   = { "default_env" => {  "adapter" => "not_postgres", "database" => "not_foo" } }
-        actual   = assert_deprecated { resolve_spec("default_env", config) }
-        expected = { "adapter"=>"postgresql", "database"=>"foo", "host"=>"localhost" }
-        assert_equal expected, actual
-      end
-
-      def test_resolver_with_database_uri_and_and_current_env_string_key_and_rails_env
-        ENV['DATABASE_URL'] = "postgres://localhost/foo"
-        ENV['RAILS_ENV'] = "foo"
-
-        config   = { "not_production" => {"adapter" => "not_postgres", "database" => "not_foo" } }
-        actual   = assert_deprecated { resolve_spec("foo", config) }
-        expected = { "adapter" => "postgresql", "database" => "foo", "host" => "localhost" }
-        assert_equal expected, actual
-      end
-
-      def test_resolver_with_database_uri_and_and_current_env_string_key_and_rack_env
-        ENV['DATABASE_URL'] = "postgres://localhost/foo"
-        ENV['RACK_ENV'] = "foo"
-
-        config   = { "not_production" => {"adapter" => "not_postgres", "database" => "not_foo" } }
-        actual   = assert_deprecated { resolve_spec("foo", config) }
-        expected = { "adapter" => "postgresql", "database" => "foo", "host" => "localhost" }
-        assert_equal expected, actual
-      end
-
       def test_resolver_with_database_uri_and_known_key
         ENV['DATABASE_URL'] = "postgres://localhost/foo"
         config   = { "production" => { "adapter" => "not_postgres", "database" => "not_foo", "host" => "localhost" } }
@@ -95,16 +67,6 @@ def test_resolver_with_database_uri_and_unknown_symbol_key
         end
       end
 
-      def test_resolver_with_database_uri_and_unknown_string_key
-        ENV['DATABASE_URL'] = "postgres://localhost/foo"
-        config   = { "not_production" => {  "adapter" => "not_postgres", "database" => "not_foo" } }
-        assert_deprecated do
-          assert_raises AdapterNotSpecified do
-           resolve_spec("production", config)
-          end
-        end
-      end
-
       def test_resolver_with_database_uri_and_supplied_url
         ENV['DATABASE_URL'] = "not-postgres://not-localhost/not_foo"
         config   = { "production" => {  "adapter" => "also_not_postgres", "database" => "also_not_foo" } }