SQLCatalog: Optimise and simplify transactional_cache_decorator.

Auto-generate cache_id, removing the risk of duplicating one.
Inline getInstanceID as it is its only caller left.
Avoid wrapping if getTransactionalVariable cannot be imported.
Avoid intermediate variables, at the cost of dupicating logic but
accelerating run-time.
Use functools.wraps .
Access _cache_sequence_number directly - these pieces of code are friends
anyway, we already set a volatile property on Catalog instance. Saves one
getattr and one call.

product/ZSQLCatalog/SQLCatalog.py

@@ -40,6 +40,7 @@ from ZODB.POSException import ConflictError
 from Products.CMFCore import permissions
 from Products.PythonScripts.Utility import allow_class
 
+from functools import wraps
 import time
 import urllib
 import string
@@ -89,38 +90,38 @@ except ImportError:
   LOG('SQLCatalog', WARNING, 'Count not import getTransactionalVariable, expect slowness.')
   def getTransactionalVariable():
     return {}
-
-def getInstanceID(instance):
-  # XXX: getPhysicalPath is overkill for a unique cache identifier.
-  # What I would like to use instead of it is:
-  #   (self._p_jar.db().database_name, self._p_oid)
-  # but database_name is not unique in at least ZODB 3.4 (Zope 2.8.8).
-  try:
-    instance_id = instance._v_physical_path
-  except AttributeError:
-    instance._v_physical_path = instance_id = instance.getPhysicalPath()
-  return instance_id
-
-class transactional_cache_decorator:
-  """
+  def transactional_cache_decorator(method):
+    return method
+else:
+  def transactional_cache_decorator(method):
+    """
     Implements singleton-style caching.
     Wrapped method must have no parameters (besides "self").
-  """
-  def __init__(self, cache_id):
-    self.cache_id = cache_id
-
-  def __call__(self, method):
-    def wrapper(wrapped_self):
-      transactional_cache = getTransactionalVariable()
-      cache_id = str((self.cache_id,
-        wrapped_self.getCacheSequenceNumber(),
-        getInstanceID(wrapped_self),
-      ))
+    """
+    cache_id = id(method)
+    @wraps(method)
+    def wrapper(self):
+      # XXX: getPhysicalPath is overkill for a unique cache identifier.
+      # What I would like to use instead of it is:
+      #   (self._p_jar.db().database_name, self._p_oid)
+      # but database_name is not unique in at least ZODB 3.4 (Zope 2.8.8).
       try:
-        result = transactional_cache[cache_id]
+        instance_id = self._v_physical_path
+      except AttributeError:
+        self._v_physical_path = instance_id = self.getPhysicalPath()
+      try:
+        return getTransactionalVariable()[(
+          cache_id,
+          self._cache_sequence_number,
+          instance_id,
+        )]
       except KeyError:
-        result = transactional_cache[cache_id] = method(wrapped_self)
-      return result
+        getTransactionalVariable()[(
+          cache_id,
+          self._cache_sequence_number,
+          instance_id,
+        )] = result = method(self)
+        return result
     return wrapper
 
 list_type_list = list, tuple, set, frozenset
@@ -944,7 +945,7 @@ class Catalog(Folder,
   def getSqlCatalogSchema(self):
     return self.sql_catalog_schema
 
-  @transactional_cache_decorator('SQLCatalog._getCatalogSchema')
+  @transactional_cache_decorator
   def _getCatalogSchema(self):
     method = getattr(self, self.sql_catalog_multi_schema, None)
     result = {}
@@ -985,7 +986,7 @@ class Catalog(Folder,
     return self._getCatalogSchema()[table]
 
   security.declarePublic('getColumnIds')
-  @transactional_cache_decorator('SQLCatalog.getColumnIds')
+  @transactional_cache_decorator
   def getColumnIds(self):
     """
     Calls the show column method and returns dictionnary of
@@ -1007,7 +1008,7 @@ class Catalog(Folder,
     return sorted(keys)
 
   security.declarePrivate('getColumnMap')
-  @transactional_cache_decorator('SQLCatalog.getColumnMap')
+  @transactional_cache_decorator
   def getColumnMap(self):
     """
     Calls the show column method and returns dictionnary of
@@ -1022,7 +1023,7 @@ class Catalog(Folder,
     return result
 
   security.declarePublic('getResultColumnIds')
-  @transactional_cache_decorator('SQLCatalog.getResultColumnIds')
+  @transactional_cache_decorator
   def getResultColumnIds(self):
     """
     Calls the show column method and returns dictionnary of
@@ -1036,7 +1037,7 @@ class Catalog(Folder,
     return sorted(keys)
 
   security.declarePublic('getSortColumnIds')
-  @transactional_cache_decorator('SQLCatalog.getSortColumnIds')
+  @transactional_cache_decorator
   def getSortColumnIds(self):
     """
     Calls the show column method and returns dictionnary of
@@ -1713,7 +1714,7 @@ class Catalog(Folder,
     """
     return self.getCatalogMethodIds(valid_method_meta_type_list=('Script (Python)', ))
 
-  @transactional_cache_decorator('SQLCatalog._getSQLCatalogRelatedKeyList')
+  @transactional_cache_decorator
   def _getSQLCatalogRelatedKeySet(self):
     column_map = self.getColumnMap()
     column_set = set(column_map)
@@ -1758,7 +1759,7 @@ class Catalog(Folder,
     """
     return self.sql_catalog_scriptable_keys
 
-  @transactional_cache_decorator('SQLCatalog.getTableIndex')
+  @transactional_cache_decorator
   def _getTableIndex(self, table):
     table_index = {}
     method = getattr(self, self.sql_catalog_index, '')
@@ -1830,7 +1831,7 @@ class Catalog(Folder,
   def getSqlCatalogScriptableKeysList(self):
     return self.sql_catalog_scriptable_keys
 
-  @transactional_cache_decorator('SQLCatalog._getgetScriptableKeyDict')
+  @transactional_cache_decorator
   def _getgetScriptableKeyDict(self):
     result = {}
     for scriptable_key_definition in self.getSqlCatalogScriptableKeysList():
@@ -2321,7 +2322,7 @@ class Catalog(Folder,
   def getSqlCatalogSearchKeysList(self):
     return self.sql_catalog_search_keys
 
-  @transactional_cache_decorator('SQLCatalog._getSearchKeyDict')
+  @transactional_cache_decorator
   def _getSearchKeyDict(self):
     result = {}
     search_key_column_dict = {
@@ -2588,7 +2589,7 @@ class Catalog(Folder,
     return ''
 
   security.declarePublic('getOptimizerSwitchKeyList')
-  @transactional_cache_decorator('SQLCatalog.getOptimizerSwitchKeyList')
+  @transactional_cache_decorator
   def getOptimizerSwitchKeyList(self):
     return [
       pair.split('=', 1)[0]