sql module was never implemented
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Salvo 'LtWorf' Tomaselli
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# -*- coding: utf-8 -*-
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# Relational
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# Copyright (C) 2009 Salvo "LtWorf" Tomaselli
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#
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# Relation is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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#
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# author Salvo "LtWorf" Tomaselli <tiposchi@tiscali.it>
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'''This module converts SQL queries into relational algebra expressions'''
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def stub():
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"NATURAL JOIN"
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"CROSS JOIN" ,
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def extract_select(query,internal=''):
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#Handling select *
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if len(query)==1 and query[0]=='*':
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return ''
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#Create dictionary for projection and rename .
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#Keys are fields to project. Value is none if no rename is needed
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pr_dic={}
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key=None
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for i in query:
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if i.lower() ==',':
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key=None
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elif key==None:
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pr_dic[i]=None
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key=i
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else:
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pr_dic[key]=i
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#Preparing string for projection and rename
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ren=''
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proj=''
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for i in pr_dic.iterkeys():
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proj+=',%s'%i
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if pr_dic[i]!=None:
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ren+=',%s➡%s'%(i,pr_dic[i])
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#Removes starting commas
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ren=ren[1:]
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proj=proj[1:]
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result='π %s (%s)' % (proj,internal)
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if len(ren)!=0:
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result='ρ %s (%s)' % (ren,result)
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return result
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def extract_from(query):
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return query
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def sql2relational(query):
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query=query.replace('\n',' ').replace(',',' , ')
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tokens=[]
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t=query.split(' ')
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escape=False
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for i in range(len(t)):
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tok=t[i].lower().strip()
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if tok=='from' and not escape:
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break
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if tok in ('select','as',','):
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escape=True
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else:
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escape=False
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return extract_select(t[1:i])
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class table(object):
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def __init__(self):
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self.attr=[]
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self.realname=None
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pass
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sqlops=('SELECT','FROM','WHERE',',',';')
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import optimizations
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if __name__=="__main__":
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query="SELECT * FROM a AS b,a WHERE a.id!= b.id and a.age<12 or b.sucation==4 or d=3;"
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query=query.replace(',',' , ').replace(';',' ; ')
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print query
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parts=query.split(' ')
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tokens=[]
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temp=''
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lastop=None
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for i in parts:
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if i in sqlops:
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# TODO must tokenize (blabla(bla)) as a single token
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if lastop == 'WHERE': #Where is a special case, must tokenize all the stuff
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for j in optimizations.tokenize_select(temp):
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tokens.append(j.strip())
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else:
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tokens.append(temp.strip())
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tokens.append(i.strip())
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temp=''
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lastop=i
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else:
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temp+=i+' '
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tokens=tokens[1:] #Removes futile 1st empty element
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print tokens
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rels={}
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from_=[]
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where_=[]
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select_=[]
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for i in tokens:
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if i in ('SELECT','FROM','WHERE'):
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last=i
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continue
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if last=='FROM':
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if ' AS ' in i:
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parts=i.split(' AS ')
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rels[parts[1].strip()]=table()
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rels[parts[1].strip()].realname=parts[0].strip()
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from_.append(parts[1].strip())
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pass
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else:
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if i!=',':
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rels[i.strip()]=table()
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from_.append(i.strip())
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pass
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elif last=='WHERE':
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where_.append(i)
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if i in optimizations.sel_op:
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continue
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if '.' in i:
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parts=i.split('.',1)
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if parts[1] not in rels[parts[0]].attr:
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rels[parts[0]].attr.append(parts[1])
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elif last=='SELECT':
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# TODO should do like the same of WHERE but supporting AS too
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pass
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for i in rels.keys():
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print "========" + i + "========"
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print rels[i].attr
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print rels[i].realname
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print from_
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for i in from_:
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if i in rels.keys():
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print i
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#print sql2relational('SELECT a,c AS q FROM from;')
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