CCF_100
/
relational
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

changed fields to attributes 

git-svn-id: http://galileo.dmi.unict.it/svn/relational/trunk@9 014f5005-505e-4b48-8d0a-63407b615a7c
master
LtWorf 2008-07-17 18:28:44 +07:00
parent 350bd00967
commit 0c11969722
1 changed files with 61 additions and 58 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

119
relation.py
Unescape Escape View File

@ -43,7 +43,7 @@ class relation (object):
def save(self,filename):
'''Saves the relation in a file'''
res=""
for f in self.header.fields:
for f in self.header.attributes:
res+="%s "%(f)
@ -57,31 +57,31 @@ class relation (object):
def selection(self,expr):
'''Selection, expr must be a valid boolean expression, can contain field names,
constant, math operations and boolean ones.'''
fields={}
attributes={}
newt=relation()
newt.header=header(list(self.header.fields))
newt.header=header(list(self.header.attributes))
for i in self.content:
for j in range(len(self.header.fields)):
for j in range(len(self.header.attributes)):
if i[j].isdigit():
fields[self.header.fields[j]]=int(i[j])
attributes[self.header.attributes[j]]=int(i[j])
else:
fields[self.header.fields[j]]=i[j]
attributes[self.header.attributes[j]]=i[j]
if eval(expr,fields):
if eval(expr,attributes):
newt.content.append(i)
return newt
def product (self,other):
'''Cartesian product, fields must be different to avoid collisions
Doing this operation on relations with colliding fields will
'''Cartesian product, attributes must be different to avoid collisions
Doing this operation on relations with colliding attributes will
cause the return of a None value.
It is possible to use rename on fields and then use the product'''
It is possible to use rename on attributes and then use the product'''
if (self.__class__!=other.__class__)or(self.header.sharedFields(other.header)!=0):
if (self.__class__!=other.__class__)or(self.header.sharedAttributes(other.header)!=0):
return None
newt=relation()
newt.header=header(self.header.fields+other.header.fields)
newt.header=header(self.header.attributes+other.header.attributes)
for i in self.content:
for j in other.content:
@ -89,23 +89,23 @@ class relation (object):
return newt
def projection(self,* fields):
def projection(self,* attributes):
'''Projection operator, takes many parameters, for each field to use.
Can also use a single parameter with a list.
Will delete duplicate items
If an empty list or no parameters are provided, returns None'''
#Parameters are supplied in a list, instead with multiple parameters
if fields[0].__class__ == list().__class__:
fields=fields[0]
if attributes[0].__class__ == list().__class__:
attributes=attributes[0]
#Avoiding duplicated fields
fields1=[]
for i in fields:
if i not in fields1:
fields1.append(i)
fields=fields1
#Avoiding duplicated attributes
attributes1=[]
for i in attributes:
if i not in attributes1:
attributes1.append(i)
attributes=attributes1
ids=self.header.getFieldsId(fields)
ids=self.header.getAttributesId(attributes)
if len(ids)==0:
return None
@ -113,7 +113,7 @@ class relation (object):
#Create the header
h=[]
for i in ids:
h.append(self.header.fields[i])
h.append(self.header.attributes[i])
newt.header=header(h)
#Create the body
@ -134,7 +134,7 @@ class relation (object):
result=[]
newt=relation()
newt.header=header(list(self.header.fields))
newt.header=header(list(self.header.attributes))
for i in range(len(params)):
if i%2==0:
@ -153,7 +153,7 @@ class relation (object):
if (self.__class__!=other.__class__)or(self.header!=other.header):
return None
newt=relation()
newt.header=header(list(self.header.fields))
newt.header=header(list(self.header.attributes))
#Adds only element not in other, duplicating them
for e in self.content:
@ -170,7 +170,7 @@ class relation (object):
if (self.__class__!=other.__class__)or(self.header!=other.header):
return None
newt=relation()
newt.header=header(list(self.header.fields))
newt.header=header(list(self.header.attributes))
#Adds only element not in other, duplicating them
for e in self.content:
@ -188,7 +188,7 @@ class relation (object):
if (self.__class__!=other.__class__)or(self.header!=other.header):
return None
newt=relation()
newt.header=header(list(self.header.fields))
newt.header=header(list(self.header.attributes))
#Adds element from self, duplicating them all
for e in self.content:
@ -198,29 +198,32 @@ class relation (object):
if e not in newt.content:
newt.content.append(list(e))
return newt
def join(self,other):
'''Natural join, using field's names'''
'''Natural join, joins on shared attributes (one or more). If there are no
shared attributes, it will behave as cartesian product.'''
shared=[]
for i in self.header.fields:
if i in other.header.fields:
for i in self.header.attributes:
if i in other.header.attributes:
shared.append(i)
newt=relation() #Creates the new relation
#Adds all the fields of the 1st relation
newt.header=header(list(self.header.fields))
#Adds all the attributes of the 1st relation
newt.header=header(list(self.header.attributes))
#Adds all the fields of the 2nd, when non shared
for i in other.header.fields:
#Adds all the attributes of the 2nd, when non shared
for i in other.header.attributes:
if i not in shared:
newt.header.fields.append(i)
newt.header.attributes.append(i)
#Shared ids of self
sid=self.header.getFieldsId(shared)
sid=self.header.getAttributesId(shared)
#Shared ids of the other relation
oid=other.header.getFieldsId(shared)
oid=other.header.getAttributesId(shared)
#Non shared ids of the other relation
noid=[]
for i in range(len(other.header.fields)):
for i in range(len(other.header.attributes)):
if i not in oid:
noid.append(i)
@ -243,7 +246,7 @@ class relation (object):
'''Returns a string representation of the relation, can be printed with
monospaced fonts'''
m_len=[] #Maximum lenght string
for f in self.header.fields:
for f in self.header.attributes:
m_len.append(len(f))
for f in self.content:
@ -255,8 +258,8 @@ class relation (object):
res=""
for f in range(len(self.header.fields)):
res+="%s"%(self.header.fields[f].ljust(2+m_len[f]))
for f in range(len(self.header.attributes)):
res+="%s"%(self.header.attributes[f].ljust(2+m_len[f]))
for r in self.content:
@ -272,46 +275,46 @@ class header (object):
'''This class defines the header of a relation.
It is used within relations to know if requested operations are accepted'''
def __init__(self,fields):
'''Accepts a list with fields' names. Names MUST be unique'''
self.fields=fields
def __init__(self,attributes):
'''Accepts a list with attributes' names. Names MUST be unique'''
self.attributes=attributes
def __repr__(self):
return "header(%s)" % (self.fields.__repr__())
return "header(%s)" % (self.attributes.__repr__())
def rename(self,old,new):
'''Renames a field. Doesn't check if it is a duplicate.
Returns True if the field was renamed, False otherwise'''
for i in range(len(self.fields)):
if self.fields[i]==old:
self.fields[i]=new
for i in range(len(self.attributes)):
if self.attributes[i]==old:
self.attributes[i]=new
return True
return False #Requested field was not found
def sharedFields(self,other):
'''Returns how many fields this header has in common with a given one'''
def sharedAttributes(self,other):
'''Returns how many attributes this header has in common with a given one'''
res=0
for i in self.fields:
if i in other.fields:
for i in self.attributes:
if i in other.attributes:
res+=1
return res
def __str__(self):
'''Returns String representation of the field's list'''
return self.fields.__str__()
return self.attributes.__str__()
def __eq__(self,other):
return self.fields==other.fields
return self.attributes==other.attributes
def __ne__(self,other):
return self.fields!=other.fields
return self.attributes!=other.attributes
def getFieldsId(self,param):
def getAttributesId(self,param):
'''Returns a list with numeric index corresponding to field's name'''
res=[]
for i in param:
for j in range(len(self.fields)):
if i==self.fields[j]:
for j in range(len(self.attributes)):
if i==self.attributes[j]:
res.append(j)
return res