Using python RediSearch client to connect to RediSearch and doing a prefix search which should match 300 documents it only returns 200 if there is another TagField in the index:
from redisearch import Client, Query, TextField, TagField
client = Client('myindex')
client.create_index([TextField('username'), TagField('age')])
# add 300 documents
for i in range(300):
client.add_document(i, username='user%s' % i, age=i)
res = client.search(Query("@username:user*"))
assert res.total == 300 # this is always 200 no matter how many documents you add.