willholley commented on a change in pull request #1719: Don't use $not to
validate use of index
URL: https://github.com/apache/couchdb/pull/1719#discussion_r238677587
##########
File path: src/mango/test/03-operator-test.py
##########
@@ -251,6 +251,16 @@ def test_gte_respsects_unicode_collation(self):
})
user_ids = [12,13,14]
self.assertUserIds(user_ids, docs)
+
+ def test_ne_returns_correct_docs(self):
+ selector = {
+ "twitter": {
+ "$ne": "@nonahorton"
+ }
+ }
+ docs = self.db.find(selector, fields=["user_id"])
+ ex = self.db.find(selector, fields=["user_id"], explain=True)
+ self.assertUserIds([0,1,9,13], docs)
Review comment:
We probably want to exercise `$not` here (even though it may be normalized
to `$ne` under the hood). For example:
```
# gotcha here is that this implicitly adds { $exists: true } for the
referenced field,
# so is not strictly the inverse of { "ordered":"A" }
def test_not_returns_expected_docs(self):
selector = {
"$not": {
"ordered": "A"
}
}
docs = self.db.find(selector, fields=["user_id"])
ex = self.db.find(selector, fields=["user_id"], explain=True)
# returns all docs that have an "ordered" field that is not equal to
"A"
self.assertUserIds([6, 7, 8, 9, 10, 11, 12, 14], docs)
```
as mentioned in the test, there is an underlying oddity/bug in Mango where
we differ from MongoDB behaviour for $not and $ne operators. [MongoDB
docs](https://docs.mongodb.com/manual/reference/operator/query/not/) state:
> $not performs a logical NOT operation on the specified
<operator-expression> and selects the documents that do not match the
<operator-expression>. This includes documents that do not contain the field.
Mango will currently only return documents that contain the field; to return
documents that do not contain the field, the user needs to add an explicit
`$exists: false` to the selector. I think this is incorrect but it's a tricky
thing to change at this point; perhaps @davisp can remember why it is this way?
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