*
     * @return true if the operation was successful, false otherwise.
     */
    public boolean deleteAllWords() {
        final SuggestDeleteResponse response = suggester.indexer().deleteAll();
        if (response.hasError()) {
            logger.warn("Failed to delete all words.", response.getErrors().get(0));
            return false;
        }
        refresh();
        return true;
    }

     * Deletes all failure URL logs.
     *
     * @return JSON response with result status
     */
    @Execute
    public JsonResponse<ApiResult> delete$all() {
        try {
            failureUrlService.deleteAll(failureUrlPager);
            failureUrlPager.clear();
            saveInfo(messages -> messages.addSuccessFailureUrlDeleteAll(GLOBAL));
        } catch (final Exception e) {

        return redirect(getClass());
    }

    /**
     * Delete all crawling info.
     * @return The HTML response.
     */
    @Execute
    @Secured({ ROLE, ROLE + VIEW })
    public HtmlResponse deleteall() {
        verifyToken(this::asListHtml);
        crawlingInfoService.deleteOldSessions(processHelper.getRunningSessionIdSet());
        crawlingInfoPager.clear();

        @Override
        public void delete(String sessionId) {
            // Do nothing in test
        }

        @Override
        public void deleteAll() {
            // Do nothing in test
        }

        @Override
        public void offerAll(String sessionId, List<OpenSearchUrlQueue> list) {
            // Do nothing in test
        }

     *
     * @param form the list form containing search criteria
     * @return HTML response redirecting to the list page
     */
    @Execute
    @Secured({ ROLE, ROLE + VIEW })
    public HtmlResponse deleteall(final ListForm form) {
        validate(form, messages -> {}, this::asListHtml);
        verifyToken(this::asListHtml);
        try {
            searchHelper.deleteByQuery(request, form);

        assertEquals(1, chain.deleteCalls.size());
        assertEquals(user, chain.deleteCalls.get(0));
    }

    // Test delete with null user
    public void test_delete_nullUser() {
        TestAuthenticationChain chain = new TestAuthenticationChain();

        chain.delete(null);

        assertEquals(1, chain.deleteCalls.size());
        assertNull(chain.deleteCalls.get(0));
    }