Mango query on python 3.8

Question

I'm trying to query a CouchDB database from Python and it works... but not entirely.

So, I created a partitioned DB with partition for movies, ratings, and tags and every partition _id is "partitionName : id".

Now I want to count the documents into ratings partition (100836 in the .csv file that I've downloaded)

After connection I do this:

mango1 = {"selector" : { "_id" : {"$regex" : "^ratings :"}}}
i = 0
for row in db.find(mango1):
    i += 1
print ("Ratings are: ", i)

It prints always 25, but from GUI I know that are more than 25 docs. How can I fix this problem? I read that Mango isn't able to count like SQL.

Answer 1

You get always 25 because the default CoucheDB limit is 25 documents.

You need to increase either

• the Limit size so that all documents are retrieved in one go or
• do some kind of pagination where you retrieve 25 documents each by using a start offset

Increase Limit of retrieved documents

To get for example 100 documents you could try this:

{"selector" : { "_id" : {"$regex" : "^ratings :"}}, "limit": 100}

Pagination A form of pagination could look like this:

{"selector" : { "_id" : {"$regex" : "^ratings :"}}, "limit": 50, "skip": 100}

This query will skip the first 100 documents and get you the following 50.