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#

# 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/>.

"""plan execution of rql queries on a single source"""

from six import text_type

from rql.stmts import Union, Select

from rql.nodes import Constant, Relation

from cubicweb import QueryError

from cubicweb.schema import VIRTUAL_RTYPES

from cubicweb.rqlrewrite import add_types_restriction

from cubicweb.server.edition import EditedEntity

READ_ONLY_RTYPES = set(('eid', 'has_text', 'is', 'is_instance_of', 'identity'))

_CONSTANT = object()

_FROM_SUBSTEP = object()

def _extract_const_attributes(plan, rqlst, to_build):

    """add constant values to entity def, mark variables to be selected

    """

    to_select = {}

    for relation in rqlst.main_relations:

        lhs, rhs = relation.get_variable_parts()

        rtype = relation.r_type

        if rtype in READ_ONLY_RTYPES:

            raise QueryError("can't assign to %s" % rtype)

        try:

            edef = to_build[str(lhs)]

        except KeyError:

            # lhs var is not to build, should be selected and added as an

            # object relation

            edef = to_build[str(rhs)]

            to_select.setdefault(edef, []).append((rtype, lhs, 1))

        else:

            if isinstance(rhs, Constant) and not rhs.uid:

                # add constant values to entity def

                value = rhs.eval(plan.args)

                eschema = edef.entity.e_schema

                attrtype = eschema.subjrels[rtype].objects(eschema)[0]

                if attrtype == 'Password' and isinstance(value, text_type):

                    value = value.encode('UTF8')

                edef.edited_attribute(rtype, value)

            elif str(rhs) in to_build:

                # create a relation between two newly created variables

                plan.add_relation_def((edef, rtype, to_build[rhs.name]))

            else:

    return to_select

def _extract_eid_consts(plan, rqlst):

    """return a dict mapping rqlst variable object to their eid if specified in

    the syntax tree

    """

    cnx = plan.cnx

    if rqlst.where is None:

        return {}

    eidconsts = {}

    neweids = cnx.transaction_data.get('neweids', ())

    checkread = cnx.read_security

    eschema = cnx.vreg.schema.eschema

    for rel in rqlst.where.get_nodes(Relation):

        # only care for 'eid' relations ...

        if (rel.r_type == 'eid'

            lhs, rhs = rel.get_variable_parts()

            if isinstance(rhs, Constant):

                eid = int(rhs.eval(plan.args))

                # check read permission here since it may not be done by

                # the generated select substep if not emited (eg nothing

                # to be selected)

                if checkread and eid not in neweids:

                    with cnx.security_enabled(read=False):

                        eschema(cnx.entity_type(eid)).check_perm(

                            cnx, 'read', eid=eid)

                eidconsts[lhs.variable] = eid

    return eidconsts

def _build_substep_query(select, origrqlst):

    """Finalize substep select query that should be executed to get proper

    selection of stuff to insert/update.

    Return None when no query actually needed, else the given select node that

    will be used as substep query.

    """

    if origrqlst.where is not None and not select.selection:

        # no selection, append one randomly by searching for a relation which is

        # not neged neither a type restriction (is/is_instance_of)

        for rel in origrqlst.where.iget_nodes(Relation):

            if not (rel.neged(traverse_scope=True) or rel.is_types_restriction()):

                select.append_selected(rel.children[0].copy(select))

                break

        else:

            return None

    if select.selection:

        if origrqlst.where is not None:

            select.set_where(origrqlst.where.copy(select))

        if getattr(origrqlst, 'having', None):

            select.set_having([sq.copy(select) for sq in origrqlst.having])

        return select

    return None

class SSPlanner(object):

    """SingleSourcePlanner: build execution plan for rql queries

    optimized for single source repositories

    """

    def __init__(self, schema, rqlhelper):

        self.schema = schema

        self.rqlhelper = rqlhelper

    def build_plan(self, plan):

        """build an execution plan from a RQL query

        do nothing here, dispatch according to the statement type

        """

        build_plan = getattr(self, 'build_%s_plan' % plan.rqlst.TYPE)

        for step in build_plan(plan, plan.rqlst):

            plan.add_step(step)

    def build_select_plan(self, plan, rqlst):

        """build execution plan for a SELECT RQL query. Suppose only one source

        is available and so avoid work need for query decomposition among sources

        the rqlst should not be tagged at this point.

        """

        plan.preprocess(rqlst)

        return (OneFetchStep(plan, rqlst),)

    def build_insert_plan(self, plan, rqlst):

        """get an execution plan from an INSERT RQL query"""

        # each variable in main variables is a new entity to insert

        to_build = {}

        cnx = plan.cnx

        etype_class = cnx.vreg['etypes'].etype_class

        for etype, var in rqlst.main_variables:

            # need to do this since entity class is shared w. web client code !

            to_build[var.name] = EditedEntity(etype_class(etype)(cnx))

            plan.add_entity_def(to_build[var.name])

        # add constant values to entity def, mark variables to be selected

        to_select = _extract_const_attributes(plan, rqlst, to_build)

        # add necessary steps to add relations and update attributes

        step.children += self._compute_relation_steps(plan, rqlst, to_select)

        return (step,)

    def _compute_relation_steps(self, plan, rqlst, to_select):

        """handle the selection of relations for an insert query"""

        eidconsts = _extract_eid_consts(plan, rqlst)

        for edef, rdefs in to_select.items():

            # create a select rql st to fetch needed data

            select = Select()

            eschema = edef.entity.e_schema

            for i, (rtype, term, reverse) in enumerate(rdefs):

                if getattr(term, 'variable', None) in eidconsts:

                    value = eidconsts[term.variable]

                else:

                    select.append_selected(term.copy(select))

                    value = _FROM_SUBSTEP

                if reverse:

                    rdefs[i] = (rtype, InsertRelationsStep.REVERSE_RELATION, value)

                else:

                    rschema = eschema.subjrels[rtype]

                    if rschema.final or rschema.inlined:

                        rdefs[i] = (rtype, InsertRelationsStep.FINAL, value)

                    else:

                        rdefs[i] = (rtype, InsertRelationsStep.RELATION, value)

            step = InsertRelationsStep(plan, edef, rdefs)

            select = _build_substep_query(select, rqlst)

            if select is not None:

                step.children += self._select_plan(plan, select, rqlst.solutions)

            yield step

    def build_delete_plan(self, plan, rqlst):

        """get an execution plan from a DELETE RQL query"""

        # build a select query to fetch entities to delete

        steps = []

        for etype, var in rqlst.main_variables:

            step = DeleteEntitiesStep(plan)

            step.children += self._sel_variable_step(plan, rqlst, etype, var)

            steps.append(step)

        for relation in rqlst.main_relations:

            step = DeleteRelationsStep(plan, relation.r_type)

            step.children += self._sel_relation_steps(plan, rqlst, relation)

            steps.append(step)

        return steps

    def _sel_variable_step(self, plan, rqlst, etype, varref):

        """handle the selection of variables for a delete query"""

        select = Select()

        varref = varref.copy(select)

        select.defined_vars = {varref.name: varref.variable}

        select.append_selected(varref)

        if rqlst.where is not None:

            select.set_where(rqlst.where.copy(select))

        if getattr(rqlst, 'having', None):

            select.set_having([x.copy(select) for x in rqlst.having])

        if etype != 'Any':

            select.add_type_restriction(varref.variable, etype)

        return self._select_plan(plan, select, rqlst.solutions)

    def _sel_relation_steps(self, plan, rqlst, relation):

        """handle the selection of relations for a delete query"""

        select = Select()

        lhs, rhs = relation.get_variable_parts()

        select.append_selected(lhs.copy(select))

        select.append_selected(rhs.copy(select))

        select.set_where(relation.copy(select))

        if rqlst.where is not None:

            select.add_restriction(rqlst.where.copy(select))

        if getattr(rqlst, 'having', None):

            select.set_having([x.copy(select) for x in rqlst.having])

        return self._select_plan(plan, select, rqlst.solutions)

    def build_set_plan(self, plan, rqlst):

        """get an execution plan from an SET RQL query"""

        getrschema = self.schema.rschema

        select = Select()   # potential substep query

        selectedidx = {}    # local state

        updatedefs = []     # definition of update attributes/relations

        # search for eid const in the WHERE clause

        eidconsts = _extract_eid_consts(plan, rqlst)

        # build `updatedefs` describing things to update and add necessary

        # variables to the substep selection

        for i, relation in enumerate(rqlst.main_relations):

            if relation.r_type in VIRTUAL_RTYPES:

                raise QueryError('can not assign to %r relation'

                                 % relation.r_type)

            lhs, rhs = relation.get_variable_parts()

            lhskey = lhs.as_string()

                if lhs.variable in eidconsts:

                    eid = eidconsts[lhs.variable]

                    lhsinfo = (_CONSTANT, eid, residx)

                else:

                    select.append_selected(lhs.copy(select))

                    lhsinfo = (_FROM_SUBSTEP, selidx, residx)

                    selidx += 1

                residx += 1

                selectedidx[lhskey] = lhsinfo

            else:

                lhsinfo = selectedidx[lhskey][:-1] + (None,)

            rhskey = rhs.as_string()

                if isinstance(rhs, Constant):

                    rhsinfo = (_CONSTANT, rhs.eval(plan.args), residx)

                elif getattr(rhs, 'variable', None) in eidconsts:

                    eid = eidconsts[rhs.variable]

                    rhsinfo = (_CONSTANT, eid, residx)

                else:

                    select.append_selected(rhs.copy(select))

                    rhsinfo = (_FROM_SUBSTEP, selidx, residx)

                    selidx += 1

                residx += 1

                selectedidx[rhskey] = rhsinfo

            else:

                rhsinfo = selectedidx[rhskey][:-1] + (None,)

            rschema = getrschema(relation.r_type)

        # the update step

        step = UpdateStep(plan, updatedefs)

        # when necessary add substep to fetch yet unknown values

        select = _build_substep_query(select, rqlst)

        if select is not None:

            # set distinct to avoid potential duplicate key error

            select.distinct = True

            step.children += self._select_plan(plan, select, rqlst.solutions)

        return (step,)

    # internal methods ########################################################

    def _select_plan(self, plan, select, solutions):

        union = Union()

        union.append(select)

        select.clean_solutions(solutions)

        add_types_restriction(self.schema, select)

        self.rqlhelper.annotate(union)

        return self.build_select_plan(plan, union)

# execution steps and helper functions ########################################

class Step(object):

    """base abstract class for execution step"""

    def __init__(self, plan):

        self.plan = plan

        self.children = []

    def execute_child(self):

        assert len(self.children) == 1

        return self.children[0].execute()

    def execute_children(self):

        for step in self.children:

            step.execute()

    def execute(self):

        """execute this step and store partial (eg this step) results"""

        raise NotImplementedError()

    def mytest_repr(self):

        """return a representation of this step suitable for test"""

        return (self.__class__.__name__,)

    def test_repr(self):

        """return a representation of this step suitable for test"""

        return self.mytest_repr() + (

            [step.test_repr() for step in self.children],)

class OneFetchStep(Step):

    """step consisting in fetching data from sources and directly returning

    results

    """

    def __init__(self, plan, union):

        Step.__init__(self, plan)

        self.union = union

    def execute(self):

        """call .syntax_tree_search with the given syntax tree on each

        source for each solution

        """

        self.execute_children()

        cnx = self.plan.cnx

        args = self.plan.args

        union = self.union

        if self.plan.cache_key is None:

            cachekey = None

        # union may have been splited into subqueries, in which case we can't

        # use plan.cache_key, rebuild a cache key

        elif isinstance(self.plan.cache_key, tuple):

            cachekey = list(self.plan.cache_key)

            cachekey[0] = union.as_string()

            cachekey = tuple(cachekey)

        else:

            cachekey = union.as_string()

        # get results for query

        source = cnx.repo.system_source

        result = source.syntax_tree_search(cnx, union, args, cachekey)

        return result

    def mytest_repr(self):

        """return a representation of this step suitable for test"""

        return (self.__class__.__name__,

                sorted((r.as_string(kwargs=self.plan.args), r.solutions)