This Data Explorer query would be a good starting point: Search for keywords across posts. It is only pulling in the post ids. The query could be altered to also pull in the post’s content. For example:
-- [params]
-- string :query
SELECT p.id as post_id, p.raw FROM posts p
LEFT JOIN post_search_data psd ON psd.post_id = p.id
WHERE psd.search_data @@ TO_TSQUERY(:query)