/usr/lib/python3/dist-packages/relational/querysplit.py is in python3-relational 2.5-1.
This file is owned by root:root, with mode 0o644.
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# Copyright (C) 2016 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 splits a query into a program.
from relational import parser
class Program:
def __init__(self, rels):
self.queries = []
self.dictionary = {} # Key is the query, value is the relation
self.vgen = vargen(rels, 'optm_')
def __str__(self):
r = ''
for q in self.queries:
r += '%s = %s' % (q[0], q[1]) + '\n'
return r.rstrip()
def append_query(self, node):
strnode = str(node)
rel = self.dictionary.get(strnode)
if rel:
return rel
qname = next(self.vgen)
self.queries.append((qname, node))
n = parser.Node()
n.kind = parser.RELATION
n.name = qname
self.dictionary[strnode] = n
return n
def _separate(node, program):
if node.kind == parser.UNARY and node.child.kind != parser.RELATION:
_separate(node.child, program)
rel = program.append_query(node.child)
node.child = rel
elif node.kind == parser.BINARY:
if node.left.kind != parser.RELATION:
_separate(node.left, program)
rel = program.append_query(node.left)
node.left = rel
if node.right.kind != parser.RELATION:
_separate(node.right, program)
rel = program.append_query(node.right)
node.right = rel
program.append_query(node)
def vargen(avoid, prefix=''):
'''
Generates temp variables.
Avoid contains variable names to skip.
'''
count = 0
while True:
r = ''
c = count
while True:
r = chr((c % 26) + 97) + r
if c < 26:
break
c //= 26
r = prefix + r
if r not in avoid:
yield r
count += 1
def split(node, rels):
'''
Split a query into a program.
The idea is that if there are duplicated subdtrees they
get executed only once.
'''
p = Program(rels)
_separate(node, p)
return str(p)
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