completed implementation of selection_inside_projection

git-svn-id: http://galileo.dmi.unict.it/svn/relational/trunk@154 014f5005-505e-4b48-8d0a-63407b615a7c

CHANGELOG

@@ -73,4 +73,5 @@
 - Optimizer generate a tree from the expression
 - Uses python-psyco when it is available
 - Ability to perform optimizations from GUI
-- Able to (temporarily) store queries with a name
+- Able to (temporarily) store queries with a name
+- Mechanism to add new kind of optimizations, without having to edit all the code

relational/optimizations.py

@@ -101,6 +101,21 @@ def selection_inside_projection(n):
     '''This function locates things like  σ j (π k(R)) and
     converts them into π k(σ j (R))'''
     changes=0
+    
+    if n.name=='σ' and n.child.name=='π':
+        changes=1
+        temp=n.prop
+        n.prop=n.child.prop
+        n.child.prop=temp
+        n.name='π'
+        n.child.name='σ'
+    
+    #recoursive scan
+    if n.kind==optimizer.UNARY:
+        changes+=selection_inside_projection(n.child)
+    elif n.kind==optimizer.BINARY:
+        changes+=selection_inside_projection(n.right)
+        changes+=selection_inside_projection(n.left)
     return changes
     
-    general_optimizations=[duplicated_select,down_to_unions_subtractions_intersections,duplicated_projection,selection_inside_projection]
+general_optimizations=[duplicated_select,down_to_unions_subtractions_intersections,duplicated_projection,selection_inside_projection]