- Added a new entrypoint system to the engine to allow "plugins" to

be stated in the query string for a URL.   Custom plugins can
be written which will be given the chance up front to alter and/or
consume the engine's URL and keyword arguments, and then at engine
create time will be given the engine itself to allow additional
modifications or event registration.  Plugins are written as a
subclass of :class:`.CreateEnginePlugin`; see that class for
details.
fixes #3536

1 files changed, 9 insertions, 1 deletions

diff --git a/lib/sqlalchemy/engine/url.py b/lib/sqlalchemy/engine/url.py
index 32e3f8a6b..9a955948a 100644
--- a/lib/sqlalchemy/engine/url.py
+++ b/lib/sqlalchemy/engine/url.py
@@ -17,7 +17,7 @@ be used directly and is also accepted directly by ``create_engine()``.
 import re
 from .. import exc, util
 from . import Dialect
-from ..dialects import registry
+from ..dialects import registry, plugins
 
 
 class URL(object):
@@ -117,6 +117,14 @@ class URL(object):
         else:
             return self.drivername.split('+')[1]
 
+    def _instantiate_plugins(self, kwargs):
+        plugin_names = util.to_list(self.query.get('plugin', ()))
+
+        return [
+            plugins.load(plugin_name)(self, kwargs)
+            for plugin_name in plugin_names
+        ]
+
     def _get_entrypoint(self):
         """Return the "entry point" dialect class.