Running the Long Text search

While performing long text searches on the radiology reports, the output for the results take long time(some times more than a day).
We did the indexing as per the documentation but need tuning on indexing, the data (Observation_fact table) has millions of records.
For example, a simple search for a word called "john" takes very long time and other phrases like "John takes " completes the query fast with 0 results