ts_headline ( [ config regconfig, ] document text, query tsquery [, options text ] ) → textDisplays, in an abbreviated form, the match(es) for the
query in the document, which must be raw text not a tsvector. Words in the document are normalized according to the specified or default configuration before matching to the query. Use of this function is discussed in Section 12.3.4, which also describes the available options.ts_headline('The fat cat ate the rat.', 'cat') → The fat <b>cat</b> ate the rat