Redisearch prefix search always returns max 200 for total for multiple fields index

Question

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.

Answer 1

See Search Query Syntax: Prefix matching

A few notes on prefix searches: As prefixes can be expanded into many many terms, use them with caution. There is no magic going on, the expansion will create a Union operation of all suffixes.

As a protective measure to avoid selecting too many terms, and block redis, which is single threaded, there are two limitations on prefix matching:

Prefixes are limited to 2 letters or more. You can change this number by using the MINPREFIX setting on the module command line.

Expansion is limited to 200 terms or less. You can change this number by using the MAXEXPANSIONS setting on the module command line.

See Run-time configuration: MAXEXPANSIONS for how to configure.