diff -r 6c2d57d1b6de -r e65873ad0371 hooks/synccomputed.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hooks/synccomputed.py	Tue Sep 16 16:39:23 2014 +0200
@@ -0,0 +1,227 @@
+# copyright 2014 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
+# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
+#
+# This file is part of CubicWeb.
+#
+# CubicWeb is free software: you can redistribute it and/or modify it under the
+# terms of the GNU Lesser General Public License as published by the Free
+# Software Foundation, either version 2.1 of the License, or (at your option)
+# any later version.
+#
+# CubicWeb is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+# FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Lesser General Public License along
+# with CubicWeb.  If not, see <http://www.gnu.org/licenses/>.
+"""Hooks for synchronizing computed attributes"""
+
+__docformat__ = "restructuredtext en"
+_ = unicode
+
+from collections import defaultdict
+
+from rql import nodes
+
+from cubicweb.server import hook
+
+
+class RecomputeAttributeOperation(hook.DataOperationMixIn, hook.Operation):
+    """Operation to recompute caches of computed attribute at commit time,
+    depending on what's have been modified in the transaction and avoiding to
+    recompute twice the same attribute
+    """
+    containercls = dict
+    def add_data(self, computed_attribute, eid=None):
+        try:
+            self._container[computed_attribute].add(eid)
+        except KeyError:
+            self._container[computed_attribute] = set((eid,))
+
+    def precommit_event(self):
+        for computed_attribute_rdef, eids in self.get_data().iteritems():
+            attr = computed_attribute_rdef.rtype
+            formula  = computed_attribute_rdef.formula
+            rql = formula.replace('Any ', 'Any X, ', 1)
+            kwargs = None
+            # add constraint on X to the formula
+            if None in eids : # recompute for all etype if None is found
+                rql += ', X is %s' % computed_attribute_rdef.subject
+            elif len(eids) == 1:
+                rql += ', X eid %(x)s'
+                kwargs = {'x': eids.pop()}
+            else:
+                rql += ', X eid IN (%s)' % ', '.join((str(eid) for eid in eids))
+            update_rql = 'SET X %s %%(value)s WHERE X eid %%(x)s' % attr
+            for eid, value in self.cnx.execute(rql, kwargs):
+                self.cnx.execute(update_rql, {'value': value, 'x': eid})
+
+
+class EntityWithCACreatedHook(hook.Hook):
+    """When creating an entity that has some computed attribute, those
+    attributes have to be computed.
+
+    Concret class of this hook are generated at registration time by
+    introspecting the schema.
+    """
+    __abstract__ = True
+    events = ('after_add_entity',)
+    # list of computed attribute rdefs that have to be recomputed
+    computed_attributes = None
+
+    def __call__(self):
+        for rdef in self.computed_attributes:
+            RecomputeAttributeOperation.get_instance(self._cw).add_data(
+                rdef, self.entity.eid)
+
+
+class RelationInvolvedInCAModifiedHook(hook.Hook):
+    """When some relation used in a computed attribute is updated, those
+    attributes have to be recomputed.
+
+    Concret class of this hook are generated at registration time by
+    introspecting the schema.
+    """
+    __abstract__ = True
+    events = ('after_add_relation', 'before_delete_relation')
+    # list of (computed attribute rdef, optimize_on) that have to be recomputed
+    optimized_computed_attributes = None
+
+    def __call__(self):
+        for rdef, optimize_on in self.optimized_computed_attributes:
+            if optimize_on is None:
+                eid = None
+            else:
+                eid = getattr(self, optimize_on)
+            RecomputeAttributeOperation.get_instance(self._cw).add_data(rdef, eid)
+
+
+class AttributeInvolvedInCAModifiedHook(hook.Hook):
+    """When some attribute used in a computed attribute is updated, those
+    attributes have to be recomputed.
+
+    Concret class of this hook are generated at registration time by
+    introspecting the schema.
+    """
+    __abstract__ = True
+    events = ('after_update_entity',)
+    # list of (computed attribute rdef, attributes of this entity type involved)
+    # that may have to be recomputed
+    attributes_computed_attributes = None
+
+    def __call__(self):
+        edited_attributes = frozenset(self.entity.cw_edited)
+        for rdef, used_attributes in self.attributes_computed_attributes.iteritems():
+            if edited_attributes.intersection(used_attributes):
+                # XXX optimize if the modified attributes belong to the same
+                # entity as the computed attribute
+                RecomputeAttributeOperation.get_instance(self._cw).add_data(rdef)
+
+
+# code generation at registration time #########################################
+
+def _optimize_on(formula_select, rtype):
+    """Given a formula and some rtype, tells whether on update of the given
+    relation, formula may be recomputed only for rhe relation's subject
+    ('eidfrom' returned), object ('eidto' returned) or None.
+
+    Optimizing is only possible when X is used as direct subject/object of this
+    relation, else we may miss some necessary update.
+    """
+    for rel in formula_select.get_nodes(nodes.Relation):
+        if rel.r_type == rtype:
+            sub = rel.get_variable_parts()[0]
+            obj = rel.get_variable_parts()[1]
+            if sub.name == 'X':
+                return 'eidfrom'
+            elif obj.name == 'X':
+                return 'eidto'
+            else:
+                return None
+
+
+class _FormulaDependenciesMatrix(object):
+    """This class computes and represents the dependencies of computed attributes
+    towards relations and attributes
+    """
+
+    def __init__(self, schema):
+        """Analyzes the schema to compute the dependencies"""
+        # entity types holding some computed attribute {etype: [computed rdefs]}
+        self.computed_attribute_by_etype = defaultdict(list)
+        # depending entity types {dep. etype: {computed rdef: dep. etype attributes}}
+        self.computed_attribute_by_etype_attrs = defaultdict(lambda: defaultdict(set))
+        # depending relations def {dep. rdef: [computed rdefs]
+        self.computed_attribute_by_relation = defaultdict(list) # by rdef
+        # Walk through all attributes definitions
+        for rdef in schema.iter_computed_attributes():
+            self.computed_attribute_by_etype[rdef.subject.type].append(rdef)
+            # extract the relations it depends upon - `rdef.formula_select` is
+            # expected to have been set by finalize_computed_attributes
+            select = rdef.formula_select
+            for rel_node in select.get_nodes(nodes.Relation):
+                rschema = schema.rschema(rel_node.r_type)
+                lhs, rhs = rel_node.get_variable_parts()
+                for sol in select.solutions:
+                    subject_etype = sol[lhs.name]
+                    if isinstance(rhs, nodes.VariableRef):
+                        object_etypes = set(sol[rhs.name] for sol in select.solutions)
+                    else:
+                        object_etypes = rschema.objects(subject_etype)
+                    for object_etype in object_etypes:
+                        if rschema.final:
+                            attr_for_computations = self.computed_attribute_by_etype_attrs[subject_etype]
+                            attr_for_computations[rdef].add(rschema.type)
+                        else:
+                            depend_on_rdef = rschema.rdefs[subject_etype, object_etype]
+                            self.computed_attribute_by_relation[depend_on_rdef].append(rdef)
+
+    def generate_entity_creation_hooks(self):
+        for etype, computed_attributes in self.computed_attribute_by_etype.iteritems():
+            regid = 'computed_attribute.%s_created' % etype
+            selector = hook.is_instance(etype)
+            yield type('%sCreatedHook' % etype,
+                       (EntityWithCACreatedHook,),
+                       {'__regid__': regid,
+                        '__select__':  hook.Hook.__select__ & selector,
+                        'computed_attributes': computed_attributes})
+
+    def generate_relation_change_hooks(self):
+        for rdef, computed_attributes in self.computed_attribute_by_relation.iteritems():
+            regid = 'computed_attribute.%s_modified' % rdef.rtype
+            selector = hook.match_rtype(rdef.rtype.type,
+                                        frometypes=(rdef.subject.type,),
+                                        toetypes=(rdef.object.type,))
+            optimized_computed_attributes = []
+            for computed_rdef in computed_attributes:
+                optimized_computed_attributes.append(
+                    (computed_rdef,
+                     _optimize_on(computed_rdef.formula_select, rdef.rtype))
+                     )
+            yield type('%sModifiedHook' % rdef.rtype,
+                       (RelationInvolvedInCAModifiedHook,),
+                       {'__regid__': regid,
+                        '__select__':  hook.Hook.__select__ & selector,
+                        'optimized_computed_attributes': optimized_computed_attributes})
+
+    def generate_entity_update_hooks(self):
+        for etype, attributes_computed_attributes in self.computed_attribute_by_etype_attrs.iteritems():
+            regid = 'computed_attribute.%s_updated' % etype
+            selector = hook.is_instance(etype)
+            yield type('%sModifiedHook' % etype,
+                       (AttributeInvolvedInCAModifiedHook,),
+                       {'__regid__': regid,
+                        '__select__':  hook.Hook.__select__ & selector,
+                        'attributes_computed_attributes': attributes_computed_attributes})
+
+
+def registration_callback(vreg):
+    vreg.register_all(globals().values(), __name__)
+    dependencies = _FormulaDependenciesMatrix(vreg.schema)
+    for hook_class in dependencies.generate_entity_creation_hooks():
+        vreg.register(hook_class)
+    for hook_class in dependencies.generate_relation_change_hooks():
+        vreg.register(hook_class)
+    for hook_class in dependencies.generate_entity_update_hooks():
+        vreg.register(hook_class)