Chapter 10: Caching of user avatar hashes (10d)

app/models.py

@@ -61,6 +61,7 @@ class User(UserMixin, db.Model):
     about_me = db.Column(db.Text())
     member_since = db.Column(db.DateTime(), default=datetime.utcnow)
     last_seen = db.Column(db.DateTime(), default=datetime.utcnow)
+    avatar_hash = db.Column(db.String(32))
 
     def __init__(self, **kwargs):
         super(User, self).__init__(**kwargs)
@@ -69,6 +70,9 @@ def __init__(self, **kwargs):
                 self.role = Role.query.filter_by(permissions=0xff).first()
             if self.role is None:
                 self.role = Role.query.filter_by(default=True).first()
+        if self.email is not None and self.avatar_hash is None:
+            self.avatar_hash = hashlib.md5(
+                self.email.encode('utf-8')).hexdigest()
 
     @property
     def password(self):
@@ -131,6 +135,8 @@ def change_email(self, token):
         if self.query.filter_by(email=new_email).first() is not None:
             return False
         self.email = new_email
+        self.avatar_hash = hashlib.md5(
+            self.email.encode('utf-8')).hexdigest()
         db.session.add(self)
         return True
 
@@ -150,7 +156,8 @@ def gravatar(self, size=100, default='identicon', rating='g'):
             url = 'https://secure.gravatar.com/avatar'
         else:
             url = 'http://www.gravatar.com/avatar'
-        hash = hashlib.md5(self.email.encode('utf-8')).hexdigest()
+        hash = self.avatar_hash or hashlib.md5(
+            self.email.encode('utf-8')).hexdigest()
         return '{url}/{hash}?s={size}&d={default}&r={rating}'.format(
             url=url, hash=hash, size=size, default=default, rating=rating)
 

migrations/versions/198b0eebcf9_caching_of_avatar_hashes.py

@@ -0,0 +1,26 @@
+"""caching of avatar hashes
+
+Revision ID: 198b0eebcf9
+Revises: d66f086b258
+Create Date: 2014-02-04 09:10:02.245503
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = '198b0eebcf9'
+down_revision = 'd66f086b258'
+
+from alembic import op
+import sqlalchemy as sa
+
+
+def upgrade():
+    ### commands auto generated by Alembic - please adjust! ###
+    op.add_column('users', sa.Column('avatar_hash', sa.String(length=32), nullable=True))
+    ### end Alembic commands ###
+
+
+def downgrade():
+    ### commands auto generated by Alembic - please adjust! ###
+    op.drop_column('users', 'avatar_hash')
+    ### end Alembic commands ###