Keyword search in users app is very slow

Overview:

In Pontifica Universidad Javeriana - Biblioteca Central when we are performing search using keyword in users app the response time is 15-20 secs as number of users are 284378 and there are 11 custom fields ** 

The issue is temporarily fixed by creating index on "customFields" field in users table in mod-users.

Additional Information:
Search query  used is:

SELECT jsonb,id FROM fsxxxxXXXX_mod_users.users WHERE ((((((((get_tsvector(f_unaccent(users.jsonb->>'username')) @@ tsquery_phrase(f_unaccent('xyz*'))) OR (get_tsvector(f_unaccent(users.jsonb->'personal'>>'firstName')) @@ tsquery_phrase(f_unaccent('xyz*')))) OR (get_tsvector(f_unaccent(users.jsonb>'personal'>>'preferredFirstName')) @@ tsquery_phrase(f_unaccent('xyz*')))) OR (get_tsvector(f_unaccent(users.jsonb>'personal'>>'lastName')) @@ tsquery_phrase(f_unaccent('xyz*')))) OR (get_tsvector(f_unaccent(users.jsonb>'personal'>>'email')) @@ tsquery_phrase(f_unaccent('xyz*')))) OR (get_tsvector(f_unaccent(users.jsonb>>'barcode')) @@ tsquery_phrase(f_unaccent('xyz*')))) OR (false /* id == invalid UUID /)) OR (get_tsvector(f_unaccent(users.jsonb->>'externalSystemId')) @@ tsquery_phrase(f_unaccent('xyz')))) OR (get_tsvector(f_unaccent(users.jsonb->>'customFields')) @@ tsquery_phrase(f_unaccent('xyz*'))) ORDER BY left(lower(f_unaccent(users.jsonb->'personal'>>'lastName')),600), lower(f_unaccent(users.jsonb>'personal'>>'lastName')), left(lower(f_unaccent(users.jsonb>'personal'>>'firstName')),600), lower(f_unaccent(users.jsonb>'personal'->>'firstName')) LIMIT 100 OFFSET 0