I come to report an issue we experienced with Atlas FTS search indexes when using mongoDB 4.4. We upgraded our M10 cluster from 4.2 to 4.4, and since then none of our search queries worked anymore.
After investigating it, we found that :
nested fields don’t work
partial searches don’t work (e.g. “covid” doesn’t match “My covid study project”
Only first level (not nested) exact matches are returned
Our FTS indexes were set as “dynamic: false” (see below). Once we switched to “dynamic: true”, everything worked again. In case it matters, we also switched from custom index names to “default” in order to avoid specifying the index on each query.
Here is our former FTS index on our “projects” collection: