Add bulk ensure_atoms method to storage

The addition of this method will make it possible
to optimize the many queries and updates that are performed
when a engine is initially having its storage unit prepared.

Part of blueprint make-things-speedy

Change-Id: Ie812abfbeca97372be05bc13e5c1059278fbbf4c

taskflow/engines/action_engine/engine.py

@@ -215,8 +215,9 @@ class ActionEngine(base.Engine):
         """Ensure all contained atoms exist in the storage unit."""
         transient = strutils.bool_from_string(
             self._options.get('inject_transient', True))
+        self.storage.ensure_atoms(
+            self._compilation.execution_graph.nodes_iter())
         for node in self._compilation.execution_graph.nodes_iter():
-            self.storage.ensure_atom(node)
             if node.inject:
                 self.storage.inject_atom_args(node.name,
                                               node.inject,

taskflow/storage.py

@@ -186,10 +186,20 @@ class Storage(object):
         with contextlib.closing(self._backend.get_connection()) as conn:
             return functor(conn, *args, **kwargs)
 
-    def ensure_atom(self, atom):
+    def ensure_atoms(self, atoms_iter):
-        """Ensure that there is an atomdetail in storage for the given atom.
+        """Ensure there is an atomdetail for **each** of the given atoms.
 
-        Returns uuid for the atomdetail that is/was created.
+        Returns list of atomdetail uuids for each atom processed.
+        """
+        atom_ids = []
+        for atom in atoms_iter:
+            atom_ids.append(self.ensure_atom(atom))
+        return atom_ids
+
+    def ensure_atom(self, atom):
+        """Ensure there is an atomdetail for the **given** atom.
+
+        Returns the uuid for the atomdetail that corresponds to the given atom.
         """
         match = misc.match_type(atom, self._ensure_matchers)
         if not match: