Method test_non_query_stmts

tests/hs2/test_fetch_first.py:373–443

Tests Impala's limited support for the FETCH_FIRST fetch orientation for non-query stmts that return a result set, such as SHOW, COMPUTE STATS, etc. The results of non-query statements are always cached entirely, and therefore, the cache can never be exhausted, i.e., FETCH_FIRST should a

(self)

  @pytest.mark.execute_serially
  @needs_session()
  def test_non_query_stmts(self):
    """Tests Impala's limited support for the FETCH_FIRST fetch orientation for
    non-query stmts that return a result set, such as SHOW, COMPUTE STATS, etc.
    The results of non-query statements are always cached entirely, and therefore,
    the cache can never be exhausted, i.e., FETCH_FIRST should always succeed.
    However, we only allow FETCH_FIRST on non-query stmts if query caching was enabled
    by the client for consistency. We use a 'show stats' stmt as a representative
    of these types of non-query stmts.
    """
    # Negative tests for the result caching option.
    self.__test_invalid_result_caching("show table stats functional.alltypes")

    # Test that FETCH_NEXT without result caching succeeds and FETCH_FIRST fails.
    # The show stmt returns exactly 25 results.
    execute_statement_req = TCLIService.TExecuteStatementReq()
    execute_statement_req.sessionHandle = self.session_handle
    execute_statement_req.confOverlay = dict()
    execute_statement_req.statement = "show table stats functional.alltypes"
    execute_statement_resp = self.hs2_client.ExecuteStatement(execute_statement_req)
    HS2TestSuite.check_response(execute_statement_resp)
    for i in range(1, 5):
      # Fetch 10 rows with the FETCH_NEXT orientation.
      expected_num_rows = 10
      if i == 3:
        expected_num_rows = 5
      if i == 4:
        expected_num_rows = 0
      self.fetch_until(execute_statement_resp.operationHandle,
                       TCLIService.TFetchOrientation.FETCH_NEXT, 10, expected_num_rows)
      # Fetch 10 rows with the FETCH_FIRST orientation, expecting an error.
      # After a failed FETCH_FIRST, the client can still resume FETCH_NEXT.
      self.fetch_fail(execute_statement_resp.operationHandle,
                      TCLIService.TFetchOrientation.FETCH_FIRST,
                      "Restarting of fetch requires enabling of query result caching")
      # The results of non-query stmts are not counted as 'cached'.
      self.__verify_num_cached_rows(0)

    # Tests that FETCH_FIRST always succeeds as long as result caching is enabled.
    # The show stmt returns exactly 25 results. The cache cannot be exhausted.
    execute_statement_req.confOverlay[self.IMPALA_RESULT_CACHING_OPT] = "1"
    execute_statement_req.statement = "show table stats functional.alltypes"
    execute_statement_resp = self.hs2_client.ExecuteStatement(execute_statement_req)
    HS2TestSuite.check_response(execute_statement_resp)
    for _ in range(1, 5):
      self.fetch_until(execute_statement_resp.operationHandle,
                       TCLIService.TFetchOrientation.FETCH_FIRST, 30, 25)
    # The results of non-query stmts are not counted as 'cached'.
    self.__verify_num_cached_rows(0)

    # Test combinations of FETCH_FIRST and FETCH_NEXT.
    # The show stmt returns exactly 25 results.
    execute_statement_req.confOverlay[self.IMPALA_RESULT_CACHING_OPT] = "1"
    execute_statement_req.statement = "show table stats functional.alltypes"
    execute_statement_resp = self.hs2_client.ExecuteStatement(execute_statement_req)
    HS2TestSuite.check_response(execute_statement_resp)
    # Fetch 10 rows.
    self.fetch_until(execute_statement_resp.operationHandle,
                     TCLIService.TFetchOrientation.FETCH_NEXT, 10)