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.