From 9cf8cc34a1db43cc0835ba6a74ca0b83b3b3a558 Mon Sep 17 00:00:00 2001
From: LtWorf <LtWorf@014f5005-505e-4b48-8d0a-63407b615a7c>
Date: Fri, 8 May 2009 15:42:02 +0000
Subject: [PATCH] work on progress on subsequent renames

git-svn-id: http://galileo.dmi.unict.it/svn/relational/trunk@155 014f5005-505e-4b48-8d0a-63407b615a7c
---
 relational/optimizations.py | 28 +++++++++++++++++++++++++++-
 relational/optimizer.py     |  4 ++--
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/relational/optimizations.py b/relational/optimizations.py
index 08af347..157c98c 100644
--- a/relational/optimizations.py
+++ b/relational/optimizations.py
@@ -117,5 +117,31 @@ def selection_inside_projection(n):
         changes+=selection_inside_projection(n.right)
         changes+=selection_inside_projection(n.left)
     return changes
+
+def subsequent_renames(n):
+    '''This function removes redoundant subsequent renames'''
+    changes=0
+    print "in"
+    if n.name=='π' and n.child.name==n.name:
+        changes=1
+        print "in-in"
+        
+        n.prop+=','+n.child.prop
+
+        _vars={}
+        for i in n.child.prop.split(','):
+            q=i.split('➡')
+            c_vars[q[0]]=q[1]
+        n.child=n.child.child
+        
     
-general_optimizations=[duplicated_select,down_to_unions_subtractions_intersections,duplicated_projection,selection_inside_projection]
+    #recoursive scan
+    if n.kind==optimizer.UNARY:
+        changes+=subsequent_renames(n.child)
+    elif n.kind==optimizer.BINARY:
+        changes+=subsequent_renames(n.right)
+        changes+=subsequent_renames(n.left)
+    return changes
+
+
+general_optimizations=[duplicated_select,down_to_unions_subtractions_intersections,duplicated_projection,selection_inside_projection,subsequent_renames]
diff --git a/relational/optimizer.py b/relational/optimizer.py
index 14399e8..bb16f70 100644
--- a/relational/optimizer.py
+++ b/relational/optimizer.py
@@ -193,8 +193,8 @@ if __name__=="__main__":
     #a= tokenize(u"π a,b (a*b)")
     #a=tokenize("(a-b*c)*(b-c)")
     print tree("σ i==2 (c ᑌ d - (aᑎb))") == tree("σ i==3 (c ᑌ d - (aᑎb))")
-    a=general_optimize("σ i==2 (c ᑌ d - (aᑎb))")
+    a=general_optimize("π age➡a(π ciccio➡age(R))")
     #a=general_optimize("σ i==2 (σ b>5 (d))")
-    print a
+    print '=========',a
     #print node(a)
     #print tokenize("(a)")
\ No newline at end of file