[electroly]

You can precompute to_tsvector() in parallel ahead of time if you're storing it in a dedicated column. CREATE INDEX runs on a single thread, including the part where it evaluates to_tsvector() for each row. If you ever need to recreate the index, it'll be faster if the tsvector is in a dedicated column.

I have a table with 30 million documents using pgsql's full text index. Creating the index takes ages, and search performance is generally very poor. The difference between creating the index with the precomputed column versus creating the index with the expression in the index itself (which is how I originally did it) was substantial.