From 9f9f5980b026fe2c43a62abb6695353f1a0ff72d Mon Sep 17 00:00:00 2001
From: John Vinyard <john.vinyard@gmail.com>
Date: Sat, 24 Jun 2017 18:23:38 -0500
Subject: [PATCH] Raise a more specific error when the model already exists

---
 featureflow/__init__.py         |  2 +-
 featureflow/model.py            | 12 ++++++++++--
 featureflow/test_integration.py |  4 ++--
 3 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/featureflow/__init__.py b/featureflow/__init__.py
index 860c765..cd5d5a3 100644
--- a/featureflow/__init__.py
+++ b/featureflow/__init__.py
@@ -1,4 +1,4 @@
-__version__ = '1.17.14'
+__version__ = '1.18.14'
 
 from model import BaseModel
 
diff --git a/featureflow/model.py b/featureflow/model.py
index ef56d95..b6d09d4 100644
--- a/featureflow/model.py
+++ b/featureflow/model.py
@@ -46,6 +46,13 @@ class NoPersistenceSettingsError(Exception):
     pass
 
 
+class ModelExistsError(Exception):
+    """
+    Error raised when a model has already been computed and persisted
+    """
+    pass
+
+
 class BaseModel(object):
     __metaclass__ = MetaModel
 
@@ -95,8 +102,9 @@ def process(cls, raise_if_exists=False, **kwargs):
             feature_key = feature.feature_key(_id, cls)
             # check if that feature is already stored
             if feature_key in cls.database:
-                raise ValueError(
-                    '{_id} is already stored in the database'.format(**locals()))
+                raise ModelExistsError(
+                    '{_id} is already stored in the database'.format(
+                        **locals()))
 
         graph = cls._build_extractor(_id)
         graph.remove_dead_nodes(cls.features.itervalues())
diff --git a/featureflow/test_integration.py b/featureflow/test_integration.py
index 7fa2824..7d16875 100644
--- a/featureflow/test_integration.py
+++ b/featureflow/test_integration.py
@@ -8,7 +8,7 @@
 
 from extractor import NotEnoughData, Aggregator, Node, InvalidProcessMethod
 from iteratornode import IteratorNode
-from model import BaseModel, NoPersistenceSettingsError
+from model import BaseModel, NoPersistenceSettingsError, ModelExistsError
 from feature import Feature, JSONFeature, CompressedFeature
 from data import *
 from bytestream import ByteStream, ByteStreamFeature
@@ -804,7 +804,7 @@ class Document(BaseModel, settings):
 
         Document.process(stream='humpty', _id='blah', raise_if_exists=True)
         # processing the same id a second time should raise an error
-        self.assertRaises(ValueError, lambda: Document.process(
+        self.assertRaises(ModelExistsError, lambda: Document.process(
             stream='humpty', _id='blah', raise_if_exists=True))
 
     def test_can_have_multiple_producer_like_nodes(self):