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Improved futile_union_intersection_subtraction, handles when a branch of subtracion has a selection 

git-svn-id: http://galileo.dmi.unict.it/svn/relational/trunk@209 014f5005-505e-4b48-8d0a-63407b615a7c
master
LtWorf 2009-08-18 10:28:34 +07:00
parent 1d6aa88805
commit 6734fc66e5
2 changed files with 14 additions and 7 deletions
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13
relational/optimizations.py
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@ -84,6 +84,8 @@ def futile_union_intersection_subtraction(n):
R ᑌ R --> R R ᑌ R --> R
R ᑎ R --> R R ᑎ R --> R
R - R --> σ False (R) R - R --> σ False (R)
σ k (R) - R --> σ False (R)
R - σ k (R) --> σ not k (R)
σ k (R) ᑌ R --> R σ k (R) ᑌ R --> R
σ k (R) ᑎ R --> σ k (R) σ k (R) ᑎ R --> σ k (R)
''' '''
@ -106,13 +108,18 @@ def futile_union_intersection_subtraction(n):
else: else:
replace_node(n,n.right) replace_node(n,n.right)
#TODO make work the following line... #TODO make work the following line...
#elif (n.name == '-' and ((n.left.name=='σ' and n.left.child==n.right) or (n.right.name=='σ' and n.right.child==n.left))): #Intersection of two equal things, but one has a selection elif (n.name == '-' and (n.right.name=='σ' and n.right.child==n.left)): #Subtraction of two equal things, but one has a selection
elif n.name=='-' and n.left==n.right:#Empty relation n.name=n.right.name
n.kind=n.right.kind
n.child=n.right.child
n.prop='(not (%s))' % n.right.prop
n.left=n.right=None
elif (n.name=='-' and ((n.left==n.right) or (n.left.name=='σ' and n.left.child==n.right)) ):#Empty relation
changes=1 changes=1
n.kind=optimizer.UNARY n.kind=optimizer.UNARY
n.name='σ' n.name='σ'
n.prop='False' n.prop='False'
n.child=n.left.get_first_leaf() n.child=n.left.get_left_leaf()
#n.left=n.right=None #n.left=n.right=None
return changes+recoursive_scan(futile_union_intersection_subtraction,n) return changes+recoursive_scan(futile_union_intersection_subtraction,n)

6
relational/parser.py
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@ -105,14 +105,14 @@ class node (object):
else: else:
return self.name return self.name
pass pass
def get_first_leaf(self): def get_left_leaf(self):
'''This function returns the most left random leaf in the tree. It is needed by some optimizations.''' '''This function returns the most left random leaf in the tree. It is needed by some optimizations.'''
if self.kind==RELATION: if self.kind==RELATION:
return self return self
elif self.kind==UNARY: elif self.kind==UNARY:
return self.child.get_first_leaf() return self.child.get_left_leaf()
elif self.kind==BINARY: elif self.kind==BINARY:
return self.left.get_first_leaf() return self.left.get_left_leaf()
def result_format(self,rels): def result_format(self,rels):