From 9ce1ee49d763dc73d6630065c2b7adbacb279ad1 Mon Sep 17 00:00:00 2001
From: Bert Blommers <info@bertblommers.nl>
Date: Sun, 12 Jan 2020 12:05:08 +0000
Subject: [PATCH] #2626 - DynamoDB - FilterExpression should ignore items with
 non-existent attribute

---
 moto/dynamodb2/comparisons.py         |  8 --------
 tests/test_dynamodb2/test_dynamodb.py | 26 ++++++++++++++++++++++++++
 2 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/moto/dynamodb2/comparisons.py b/moto/dynamodb2/comparisons.py
index 69d7f74e0..372f612c3 100644
--- a/moto/dynamodb2/comparisons.py
+++ b/moto/dynamodb2/comparisons.py
@@ -979,8 +979,6 @@ class OpLessThan(Op):
         # In python3 None is not a valid comparator when using < or > so must be handled specially
         if lhs and rhs:
             return lhs < rhs
-        elif lhs is None and rhs:
-            return True
         else:
             return False
 
@@ -994,8 +992,6 @@ class OpGreaterThan(Op):
         # In python3 None is not a valid comparator when using < or > so must be handled specially
         if lhs and rhs:
             return lhs > rhs
-        elif lhs and rhs is None:
-            return True
         else:
             return False
 
@@ -1027,8 +1023,6 @@ class OpLessThanOrEqual(Op):
         # In python3 None is not a valid comparator when using < or > so must be handled specially
         if lhs and rhs:
             return lhs <= rhs
-        elif lhs is None and rhs or lhs is None and rhs is None:
-            return True
         else:
             return False
 
@@ -1042,8 +1036,6 @@ class OpGreaterThanOrEqual(Op):
         # In python3 None is not a valid comparator when using < or > so must be handled specially
         if lhs and rhs:
             return lhs >= rhs
-        elif lhs and rhs is None or lhs is None and rhs is None:
-            return True
         else:
             return False
 
diff --git a/tests/test_dynamodb2/test_dynamodb.py b/tests/test_dynamodb2/test_dynamodb.py
index 831538054..b63a7c19e 100644
--- a/tests/test_dynamodb2/test_dynamodb.py
+++ b/tests/test_dynamodb2/test_dynamodb.py
@@ -1719,6 +1719,32 @@ def test_scan_filter4():
     assert response["Count"] == 0
 
 
+@mock_dynamodb2
+def test_scan_filter_should_not_return_non_existing_attributes():
+    table_name = "my-table"
+    item = {"partitionKey": "pk-2", "my-attr": 42}
+    # Create table
+    res = boto3.resource("dynamodb")
+    res.create_table(
+        TableName=table_name,
+        KeySchema=[{"AttributeName": "partitionKey", "KeyType": "HASH"}],
+        AttributeDefinitions=[{"AttributeName": "partitionKey", "AttributeType": "S"}],
+        BillingMode="PAY_PER_REQUEST",
+    )
+    table = res.Table(table_name)
+    # Insert items
+    table.put_item(Item={"partitionKey": "pk-1"})
+    table.put_item(Item=item)
+    # Verify a few operations
+    # Assert we only find the item that has this attribute
+    table.scan(FilterExpression=Attr("my-attr").lt(43))["Items"].should.equal([item])
+    table.scan(FilterExpression=Attr("my-attr").lte(42))["Items"].should.equal([item])
+    table.scan(FilterExpression=Attr("my-attr").gte(42))["Items"].should.equal([item])
+    table.scan(FilterExpression=Attr("my-attr").gt(41))["Items"].should.equal([item])
+    # Sanity check that we can't find the item if the FE is wrong
+    table.scan(FilterExpression=Attr("my-attr").gt(43))["Items"].should.equal([])
+
+
 @mock_dynamodb2
 def test_bad_scan_filter():
     client = boto3.client("dynamodb", region_name="us-east-1")