如果集合中的前一个文档包含某个值，我如何不创建新文档？

Question

I am using the python library to programmatically create documents in a collection as such:

user = client.query(q.create(q.collection("my_collection"), {
             "data": {
                     "UTC_datetime": str(datetime.now(pytz.UTC)),
                     "item_one": str(value_one),
                     "item_two": str(value_two),
                     "item_three": str(value_three)
         }
     }))

Upon certain conditions being met the python app executes again.

If item_two on the next app execution has the same value again I do not want a new document to be created.

How do I craft the above query to perform this?

Currently, I am reading the previous document, extracting the value from item_two and performing an if/else statement to either proceed to store a new document or sys.exit() .

I'm positive there is a more elegant solution that is based within Fauna's logic instead of Python's, however, I have not been able to achieve this.

Answer 1

You can create a unique index ( https://docs.fauna.com/fauna/current/api/fql/indexes ) for item_two to ensure that duplicates are not possible. You may also want to an upsert implementation

https://forums.fauna.com/t/multi-document-upsert/488/3

https://forums.fauna.com/t/does-fauna-supports-upserts/208

q.If(
   q.Exists(q.Match(q.Index('unique_item_two'), str(value_two))), 
   q.Update(...),
   q.Create(...)
)