=> select to_tsvector('examples') @@ websearch_to_tsquery('example');
 ?column? 
----------
 t
(1 row)

$ sqlfluff parse test-search.sql 
[L:  1, P:  1]      |file:
[L:  1, P:  1]      |    statement:
[L:  1, P:  1]      |        select_statement:
[L:  1, P:  1]      |            select_clause:
[L:  1, P:  1]      |                keyword:                                      'select'
[L:  1, P:  7]      |                [META] indent:
[L:  1, P:  7]      |                whitespace:                                   ' '
[L:  1, P:  8]      |                select_clause_element:
[L:  1, P:  8]      |                    function:
[L:  1, P:  8]      |                        function_name:
[L:  1, P:  8]      |                            function_name_identifier:         'to_tsvector'
[L:  1, P: 19]      |                        bracketed:
[L:  1, P: 19]      |                            start_bracket:                    '('
[L:  1, P: 20]      |                            [META] indent:
[L:  1, P: 20]      |                            expression:
[L:  1, P: 20]      |                                quoted_literal:               "'examples'"
[L:  1, P: 30]      |                            [META] dedent:
[L:  1, P: 30]      |                            end_bracket:                      ')'
[L:  1, P: 31]      |                whitespace:                                   ' '
[L:  1, P: 32]      |                unparsable:                                   !! Expected: 'Nothing...'
[L:  1, P: 32]      |                    raw:                                      '@'
[L:  1, P: 33]      |                    raw:                                      '@'
[L:  1, P: 34]      |                    whitespace:                               ' '
[L:  1, P: 35]      |                    code:                                     'websearch_to_tsquery'
[L:  1, P: 55]      |                    bracketed:
[L:  1, P: 55]      |                        start_bracket:                        '('
[L:  1, P: 56]      |                        single_quote:                         "'example'"
[L:  1, P: 65]      |                        end_bracket:                          ')'
[L:  1, P: 66]      |            [META] dedent:
[L:  1, P: 66]      |    statement_terminator:                                     ';'
[L:  1, P: 67]      |    newline:                                                  '\n'
[L:  2, P:  1]      |    [META] end_of_file:

==== parsing violations ====
L:   1 | P:  32 |  PRS | Line 1, Position 32: Found unparsable section: "@@
                       | websearch_to_tsquery('example')"
WARNING: Parsing errors found and dialect is set to 'postgres'. Have you configured your dialect correctly?

$ sqlfluff --version
sqlfluff, version 2.0.7
$ python --version
Python 3.10.6