counting changes on the tree

git-svn-id: http://galileo.dmi.unict.it/svn/relational/trunk@138 014f5005-505e-4b48-8d0a-63407b615a7c

CHANGELOG

@@ -70,3 +70,4 @@
 - Document about complexity of operations
 - Bug: error in update operation, it changed the original tuple, so also other relations using the same tuple would change. Now it copies it.
 - Added make install and uninstall
+- Optimizer generate a tree from the expression

relational/optimizations.py

@@ -24,20 +24,23 @@ within a cycle.'''
 import optimizer
 
 def duplicated_select(n):
+    changes=0
     '''This function locates and deletes things like
     σ a ( σ a(C)) and the ones like σ a ( σ b(C))'''
     if n.name=='σ' and n.child.name=='σ':        
         if n.prop != n.child.prop: #Nested but different, joining them
             n.prop = n.prop + " and " + n.child.prop
         n.child=n.child.child
-        duplicated_select(n)
+        changes=1
+        changes+=duplicated_select(n)
+        
 
     #recoursive scan
     if n.kind==optimizer.UNARY:
-        duplicated_select(n.child)
+        changes+=duplicated_select(n.child)
     elif n.kind==optimizer.BINARY:
-        duplicated_select(n.right)
-        duplicated_select(n.left)
-    return n
+        changes+=duplicated_select(n.right)
+        changes+=duplicated_select(n.left)
+    return changes
 
 general_optimizations=[duplicated_select]

relational/optimizer.py

@@ -165,7 +165,7 @@ def general_optimize(expression):
     know the fields used by the relations'''
     n=tree(expression) #Gets the tree
     for i in optimizations.general_optimizations:
-        n=i(n) #Performs the optimization
+        print "Changes done: ", i(n) #Performs the optimization
     return n.__str__()
 
 if __name__=="__main__":
@@ -178,6 +178,7 @@ if __name__=="__main__":
     #a= tokenize(u"π a,b (a*b)")
     #a=tokenize("(a-b*c)*(b-c)")
     a=general_optimize("σ i==2 (σ b>5 ( σ a>2 (C))) * σ a>2 ( σ a>2 (C))")
+    #a=general_optimize("σ i==2 (σ b>5 (d))")
     print a
     #print node(a)
     #print tokenize("(a)")