python-relational 1.2-2 / usr / share / pyshared / relational / optimizer.py

# -*- coding: utf-8 -*-
# coding=UTF-8
# Relational
# Copyright (C) 2008  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 optimizes relational expressions into ones that require less time to be executed.
#
# expression: In all the functions expression can be either an UTF-8 encoded string, containing a valid
# relational query, or it can be a parse tree for a relational expression (ie: class parser.node).
# The functions will always return a string with the optimized query, but if a parse tree was provided,
# the parse tree itself will be modified accordingly.

import optimizations
import parser


# Stuff that was here before, keeping it for compatibility
RELATION = parser.RELATION
UNARY = parser.UNARY
BINARY = parser.BINARY


b_operators = parser.b_operators
u_operators = parser.u_operators
op_functions = parser.op_functions
node = parser.node
tokenize = parser.tokenize
tree = parser.tree
# End of the stuff


def optimize_all(expression, rels, specific=True, general=True, debug=None):
    '''This function performs all the available optimizations.

    expression : see documentation of this module
    rels: dic with relation name as key, and relation istance as value
    specific: True if it has to perform specific optimizations
    general: True if it has to perform general optimizations
    debug: if a list is provided here, after the end of the function, it
        will contain the query repeated many times to show the performed
        steps.

    Return value: this will return an optimized version of the expression'''
    if isinstance(expression, unicode):
        n = tree(expression)  # Gets the tree
    elif isinstance(expression, node):
        n = expression
    else:
        raise (TypeError("expression must be a unicode string or a node"))

    if isinstance(debug, list):
        dbg = True
    else:
        dbg = False

    total = 1
    while total != 0:
        total = 0
        if specific:
            for i in optimizations.specific_optimizations:
                res = i(n, rels)  # Performs the optimization
                if res != 0 and dbg:
                    debug.append(n.__str__())
                total += res
        if general:
            for i in optimizations.general_optimizations:
                res = i(n)  # Performs the optimization
                if res != 0 and dbg:
                    debug.append(n.__str__())
                total += res
    return n.__str__()


def specific_optimize(expression, rels):
    '''This function performs specific optimizations. Means that it will need to
    know the fields used by the relations.

    expression : see documentation of this module
    rels: dic with relation name as key, and relation istance as value

    Return value: this will return an optimized version of the expression'''
    return optimize_all(expression, rels, specific=True, general=False)


def general_optimize(expression):
    '''This function performs general optimizations. Means that it will not need to
    know the fields used by the relations

    expression : see documentation of this module

    Return value: this will return an optimized version of the expression'''
    return optimize_all(expression, None, specific=False, general=True)

if __name__ == "__main__":
    # n=node(u"((a ᑌ b) - c ᑌ d) - b")
    # n=node(u"π a,b (d-a*b)")

    # print n.__str__()
    # a= tokenize("(a - (a ᑌ b) * π a,b (a-b)) - ρ 123 (a)")
    # a= tokenize(u"π a,b (a*b)")
    # a=tokenize("(a-b*c)*(b-c)")

    import relation
    import optimizations

    '''rels={}
    rels["P1"]= relation.relation("/home/salvo/dev/relational/trunk/samples/people.csv")
    rels["P2"]= relation.relation("/home/salvo/dev/relational/trunk/samples/people.csv")
    rels["R1"]= relation.relation("/home/salvo/dev/relational/trunk/samples/person_room.csv")
    rels["R2"]= relation.relation("/home/salvo/dev/relational/trunk/samples/person_room.csv")
    rels["D1"]= relation.relation("/home/salvo/dev/relational/trunk/samples/dates.csv")
    rels["S1"]= relation.relation("/home/salvo/dev/relational/trunk/samples/skillo.csv")
    print rels'''
    n = tree(u"π indice,qq,name (ρ age➡qq,id➡indice (P1-P2))")
    # n=tree("σ id==3 and indice==2 and name==5 or name<2(P1 * S1)")
    print n
    print n.toPython()

    # print optimizations.selection_and_product(n,rels)

    '''
    σ skill=='C' (π id,name,chief,age (σ chief==i and age>a (ρ id➡i,age➡a(π id,age(people))*people)) ᐅᐊ skills)
    (π id,name,chief,age (σ chief == i  and age > a  ((ρ age➡a,id➡i (π id,age (people)))*people)))ᐅᐊ(σ skill == 'C'  (skills))
    '''

    # print specific_optimize("σ name==skill and age>21 and id==indice and
    # skill=='C'(P1ᐅᐊS1)",rels)

    # print n
    # print n.result_format(rels)
    '''σ k (r) ᑌ r with r
    σ k (r) ᑎ r with σ k (r)'''

    # a=general_optimize('π indice,qq,name (ρ age➡qq,id➡indice (P1-P2))')
    # a=general_optimize("σ i==2 (σ b>5 (d))")
    # print a
    # print node(a)
    # print tokenize("(a)")