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relational
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Reduce amount of useless copies 

In case of a rename, the original relation and the resulting relations
are pointing to the same set.

In case of functions that change the relation, such as insert, a copy is
created to be able to write on it. But when writing on the other relation
a new copy would have been made too.

This fixes it, now when changing one relation, the other is marked as
writable as well.
master
Salvo 'LtWorf' Tomaselli 2015-11-18 00:05:01 +07:00
parent ff3a5935fc
commit 521ffd5d41
1 changed files with 18 additions and 4 deletions
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22
relational/relation.py
Unescape Escape View File

@ -54,6 +54,7 @@ class Relation (object):
def __init__(self, filename=""):
self._readonly = False
self._copy = None
self.content = set()
if len(filename) == 0: # Empty relation
@ -64,15 +65,29 @@ class Relation (object):
self.header = Header(next(reader)) # read 1st line
iterator = ((self.insert(i) for i in reader))
deque(iterator, maxlen=0)
def _make_duplicate(self, copy):
'''Flag that the relation "copy" is pointing
to the same set as this relation.'''
self._readonly = True
copy._readonly = True
copy._copy = self
self._copy = copy
def _make_writable(self, copy_content=True):
'''If this relation is marked as readonly, this
method will copy the content to make it writable too'''
method will copy the content to make it writable too
if copy_content is set to false, the caller must
separately copy the content.'''
if self._readonly:
self._readonly = False
self._copy._readonly = False
self._copy = None
if copy_content:
self.content = set(self.content)
self._readonly = False
def __iter__(self):
return iter(self.content)
@ -195,8 +210,7 @@ class Relation (object):
newt.header = self.header.rename(params)
newt.content = self.content
newt._readonly = True
self._readonly = True
self._make_duplicate(newt)
return newt
def intersection(self, other):