Removed unmaintained parallel module

The module is unmaintained and in any case, does not limit the
amount of parallel jobs.

relational/parallel.py

@@ -1,117 +0,0 @@
-# -*- coding: utf-8 -*-
-# Relational
-# Copyright (C) 2009  Salvo "LtWorf" Tomaselli
-#
-# Relational is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program 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 General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-#
-# author Salvo "LtWorf" Tomaselli <tiposchi@tiscali.it>
-#
-# This module offers capability of executing relational queries in parallel.
-
-import optimizer
-import multiprocessing
-import parser
-
-
-def execute(tree, rels):
-    '''This funcion executes a query in parallel.
-    Tree is the tree describing the query (usually obtained with
-    parser.tree(querystring)
-    rels is a dictionary containing the relations associated with the names'''
-
-    q = multiprocessing.Queue()
-    p = multiprocessing.Process(target=__p_exec__, args=(tree, rels, q,))
-    p.start()
-    result = q.get()
-    p.join()
-    return result
-
-
-def __p_exec__(tree, rels, q):
-    '''q is the queue used for communication'''
-    if tree.kind == parser.RELATION:
-        q.put(rels[tree.name])
-    elif tree.kind == parser.UNARY:
-
-        # Obtain the relation
-        temp_q = multiprocessing.Queue()
-        __p_exec__(tree.child, rels, temp_q)
-        rel = temp_q.get()
-
-        # Execute the query
-        result = __p_exec_unary__(tree, rel)
-        q.put(result)
-    elif tree.kind == parser.BINARY:
-        left_q = multiprocessing.Queue()
-        left_p = multiprocessing.Process(
-            target=__p_exec__, args=(tree.left, rels, left_q,))
-        right_q = multiprocessing.Queue()
-        right_p = multiprocessing.Process(
-            target=__p_exec__, args=(tree.right, rels, right_q,))
-
-        # Spawn the children
-        left_p.start()
-        right_p.start()
-
-        # Get the left and right relations
-        left = left_q.get()
-        right = right_q.get()
-
-        # Wait for the children to terminate
-        left_p.join()
-        right_p.join()
-
-        result = __p_exec_binary__(tree, left, right)
-        q.put(result)
-    return
-
-
-def __p_exec_binary__(tree, left, right):
-    if tree.name == '*':
-        return left.product(right)
-    elif tree.name == '-':
-        return left.difference(right)
-    elif tree.name == 'ᑌ':
-        return left.union(right)
-    elif tree.name == 'ᑎ':
-        return left.intersection(right)
-    elif tree.name == '÷':
-        return left.division(right)
-    elif tree.name == 'ᐅᐊ':
-        return left.join(right)
-    elif tree.name == 'ᐅLEFTᐊ':
-        return left.outer_left(right)
-    elif tree.name == 'ᐅRIGHTᐊ':
-        return left.outer_right(right)
-    else:  # tree.name=='ᐅFULLᐊ':
-        return left.outer(right)
-
-
-def __p_exec_unary__(tree, rel):
-    if tree.name == 'π':  # Projection
-        tree.prop = tree.prop.replace(' ', '').split(',')
-        result = rel.projection(tree.prop)
-    elif tree.name == "ρ":  # Rename
-        # tree.prop='{\"%s\"}' %
-        # tree.prop.replace(',','\",\"').replace('➡','\":\"').replace(' ','')
-        d = {}
-        tree.prop = tree.prop.replace(' ', '')
-        for i in tree.prop.split(','):
-            rename_ = i.split('➡')
-            d[rename_[0]] = rename_[1]
-
-        result = rel.rename(d)
-    else:  # Selection
-        result = rel.selection(tree.prop)
-    return result