Meilisearch: Getting slower the longer the query is

[arkste]

Describe the bug
While MeiliSearch is instant with 1-3 words, its getting way slower the longer the query is.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://crates.meilisearch.com
2. Type in _"this is a test to see if meilisearch is getting slower the more words i use, yep, its getting slower and slower"_
3. Never receive a response, because there will be a timeout after 30 seconds

Considering that there are ~31k entries in the database, that is a really poor search performance.
In our testing we saw a exponentially search performance degradation after around 40 chars.
Alternatively you can reproduce the issue with 0.13.0 and the movies dataset.

Expected behavior
The length of the query shouldn't have that much of an impact on the search performance (when below 1.000.000 items in the database).

[LegendreM]

hello @arkste we are continually working on performances improvement, and this limit will be pushed back in a engine refacto we are working on.
An other thing is to provide a max_query_word setting (#941) to allow user to choose the number of words accepted in a query.

thanks for your issue BTW