Use SQL statement for summing up weights

* Update models: Bill.pay_each()
* Import sql func
* reformatted using black
* Added ModelsTestCase.test_bill_pay_each() in order to test the SQL query change within pay_each.
Had to add Project.ProjectQuery.get_by_name() for the test.

1 files changed, 11 insertions, 2 deletions

diff --git a/ihatemoney/models.py b/ihatemoney/models.py
index 8a7e273..4d32fd9 100644
--- a/ihatemoney/models.py
+++ b/ihatemoney/models.py
@@ -6,6 +6,7 @@ from flask import g, current_app
 
 from debts import settle
 from sqlalchemy import orm
+from sqlalchemy.sql import func
 from itsdangerous import (
     TimedJSONWebSignatureSerializer,
     URLSafeSerializer,
@@ -17,6 +18,9 @@ db = SQLAlchemy()
 
 
 class Project(db.Model):
+    class ProjectQuery(BaseQuery):
+        def get_by_name(self, name):
+            return Project.query.filter(Project.name == name).one()
 
     id = db.Column(db.String(64), primary_key=True)
 
@@ -25,6 +29,8 @@ class Project(db.Model):
     contact_email = db.Column(db.String(128))
     members = db.relationship("Person", backref="project")
 
+    query_class = ProjectQuery
+
     @property
     def _to_serialize(self):
         obj = {
@@ -388,8 +394,11 @@ class Bill(db.Model):
     def pay_each(self):
         """Compute what each share has to pay"""
         if self.owers:
-            # FIXME: SQL might do that more efficiently
-            weights = sum(i.weight for i in self.owers)
+            weights = (
+                db.session.query(func.sum(Person.weight))
+                .join(billowers, Bill)
+                .filter(Bill.id == self.id)
+            ).scalar()
             return self.amount / weights
         else:
             return 0