Search a string across all columns of a query result
A database is not a fancy mechanism to grep. This is a horrible idea don't do this ever. That said you can convert the row object to a tsvector using Full Text Search

SELECT to_tsvector(to_jsonb(t)) @@ 'bar'
FROM ( VALUES ('foo','bar','baz') ) AS t(a,b,c); 


or you can search it as if it was text.

SELECT t::text LIKE '%bar%'
FROM ( VALUES ('foo','bar','baz') ) AS t(a,b,c);