diff --git a/createdb.py b/createdb.py
deleted file mode 100644
index cc5c501..0000000
--- a/createdb.py
+++ /dev/null
@@ -1,5 +0,0 @@
-import forget
-
-from app import db
-
-db.create_all()
diff --git a/migrations/versions/e036b007017c_.py b/migrations/versions/e036b007017c_.py
new file mode 100644
index 0000000..033dd65
--- /dev/null
+++ b/migrations/versions/e036b007017c_.py
@@ -0,0 +1,28 @@
+"""empty message
+
+Revision ID: e036b007017c
+Revises: 9fab742962ef
+Create Date: 2017-08-01 22:45:28.450097
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = 'e036b007017c'
+down_revision = '9fab742962ef'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.add_column('accounts', sa.Column('last_delete', sa.DateTime(), server_default='epoch', nullable=True))
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_column('accounts', 'last_delete')
+    # ### end Alembic commands ###
diff --git a/model.py b/model.py
index 1f38ec6..6165e2f 100644
--- a/model.py
+++ b/model.py
@@ -51,18 +51,26 @@ class Account(TimestampMixin, RemoteIDMixin):
     remote_avatar_url = db.Column(db.String)
 
     last_fetch = db.Column(db.DateTime, server_default='epoch')
+    last_delete = db.Column(db.DateTime, server_default='epoch')
 
     def touch_fetch(self):
         self.last_fetch = db.func.now()
 
+    @db.validates('policy_keep_younger', 'policy_delete_every')
+    def validate_intervals(self, key, value):
+        if not (value == timedelta(0) or value >= timedelta(minutes=1)):
+            value = timedelta(minutes=1)
+        return value
+
     # backref: tokens
     # backref: twitter_archives
+    # backref: posts
 
     def __repr__(self):
         return f"<Account({self.id}, {self.remote_screen_name}, {self.remote_display_name})>"
 
     def post_count(self):
-        return Post.query.filter(Post.author_id == self.id).count()
+        return Post.query.with_parent(self).count()
 
 
 class Account(Account, db.Model):
@@ -93,7 +101,8 @@ class Post(db.Model, TimestampMixin, RemoteIDMixin):
     body = db.Column(db.String)
 
     author_id = db.Column(db.String, db.ForeignKey('accounts.id'))
-    author = db.relationship(Account)
+    author = db.relationship(Account,
+            backref=db.backref('posts', order_by=lambda: db.desc(Post.created_at)))
 
 class TwitterArchive(db.Model, TimestampMixin):
     __tablename__ = 'twitter_archives'