Highlighting search results with Textacular
May 2022
It’s possible to leverage Postgres’s ts_headline1 to add highlighting of
matched fragments in search results. With a caveat, the search fields need to
be declared ahead of time.
To highlight a basic_search each column to be highlighted needs to be
SELECT-ed using ts_headline with the query string parsed with
plainto_tsquery.
class Post < ApplicationRecord
def self.search(query)
basic_search(title: query)
.select("#{sanitize_sql_array(["ts_headline(title, plainto_tsquery(?))", query])} as title_highlighted")
end
end
Using this blog’s post titles for testing we see:
[0] pry(main)> Post.search("server Rack").map(&:attributes)
Post Load (3.1ms) SELECT "posts".*, COALESCE(ts_rank(to_tsvector('english', "posts"."title"::text), plainto_tsquery('english', 'server\ Rack'::text)), 0) AS "rank35483819984107261", ts_headline(title, plainto_tsquery('server Rack')) as title_highlighted FROM "posts" WHERE (to_tsvector('english', "posts"."title"::text) @@ plainto_tsquery('english', 'server\ Rack'::text)) ORDER BY "rank35483819984107261" DESC
=> [{"id"=>4,
"title"=>"Server-sent events with Rails and Rack hijack",
"created_at"=>Mon, 30 May 2022 17:30:29.806047000 UTC +00:00,
"updated_at"=>Mon, 30 May 2022 17:30:29.806047000 UTC +00:00,
"rank35483819984107261"=>0.085297264,
"title_highlighted"=>"<b>Server</b>-sent events with Rails and <b>Rack</b> hijack"}]
To work for an advanced_search the query string should be passed to
to_tsquery and web_search to websearch_to_tsquery.