From 1b093691985ce0be0bcf0541bdd3b5ecb30887ce Mon Sep 17 00:00:00 2001
From: LtWorf <LtWorf@014f5005-505e-4b48-8d0a-63407b615a7c>
Date: Thu, 25 Dec 2008 11:26:40 +0000
Subject: [PATCH] Relation module has SQL-like delete

git-svn-id: http://galileo.dmi.unict.it/svn/relational/trunk@75 014f5005-505e-4b48-8d0a-63407b615a7c
---
 CHANGELOG   |  1 +
 relation.py | 21 +++++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/CHANGELOG b/CHANGELOG
index 6cda88a..e82223a 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -51,3 +51,4 @@
 - New default relation's format is csv, as defined in RFC4180
 - Converted sample's relations to csv
 - Deb postinstall generates optimized files, this will increase loading speed
+- Relation module has SQL-like delete
diff --git a/relation.py b/relation.py
index 199a3f0..8224f2a 100644
--- a/relation.py
+++ b/relation.py
@@ -417,6 +417,27 @@ class relation (object):
                 col+=1
             
         return res
+
+    def delete(self,expr):
+        '''Delete, expr must be a valid boolean expression, can contain field names,
+        constant, math operations and boolean ones.
+        This operation will change the relation itself instead of generating a new one,
+        deleting all the touples that make expr true.'''
+        attributes={}
+        new_content=[] #New content of the relation
+        for i in self.content:
+            for j in range(len(self.header.attributes)):
+                if i[j].isdigit():
+                    attributes[self.header.attributes[j]]=int(i[j])
+                elif rstring(i[j]).isFloat():
+                    attributes[self.header.attributes[j]]=float(i[j])
+                elif isDate(i[j]):
+                    attributes[self.header.attributes[j]]=rdate(i[j])
+                else:
+                    attributes[self.header.attributes[j]]=i[j]
+            if not eval(expr,attributes):
+                new_content.append(i)
+        self.content=new_content
     
 class header (object):
     '''This class defines the header of a relation.