def get(self, timestamp):
"""Get the TSDBRow located at timestamp.
.. note::
The timestamp of the returned row may be different from the
timestamp requested. This is due to the fact that the application
storing the row used an actual timestamp but the query refers to
the slot in which the timestamp argument falls.
.. note::
If an invalid row is fetched, the timestamp is set to the
requested timestamp since an invalid row has a timestamp of 0.
.. note::
If the chunk does not exist it is created with all zeros and thus
an invalid row is returned. For the current use case creating the
chunk is acceptable as the datasets are not expected to be sparse.
"""
slot = calculate_slot(timestamp, self.metadata['STEP'])
try:
min_slot = calculate_slot(self.min_timestamp(), self.metadata['STEP'])
if slot < min_slot:
raise TSDBVarRangeError(
"%d is less than the minimum slot %d" % (timestamp, min_slot))
max_slot = calculate_slot(self.max_timestamp(), self.metadata['STEP']) + self.metadata['STEP'] - 1
if slot > max_slot:
raise TSDBVarRangeError(
"%d is greater than the maximum slot %d" % (timestamp, max_slot))
except TSDBVarEmpty:
raise TSDBVarRangeError(timestamp)
try:
chunk = self._chunk(timestamp)
val = chunk.read_row(timestamp)
except TSDBVarChunkDoesNotExistError:
val = self.type.get_invalid_row()
if not val.flags & ROW_VALID:
# if row isn't valid the timestamp is 0
# set the timestamp to the slot timestamp instead
val.timestamp = timestamp
return val
def select_generator(var, begin, end, flags):
current = calculate_slot(begin, self.metadata['STEP'])
max_ts = self.max_timestamp()
now = int(time.time())
if max_ts > now:
max_ts = now
while current <= end:
try:
row = var.get(current)
except TSDBVarRangeError:
# looking for data beyond the end of recorded data so stop.
if current > max_ts:
raise StopIteration
if row.timestamp > end:
break
if not flags or row.flags & flags == flags:
yield row
current += var.metadata['STEP']
raise StopIteration
def test_calculate_slot():
for (raw, expected, step) in (
(0, 0, 30),
(1, 0, 30),
(29, 0, 30),
(30, 30, 30),
):
assert calculate_slot(raw, step) == expected
def test_calculate_slot():
for (raw, expected, step) in (
(0, 0, 30), (1, 0, 30),
(29, 0, 30), (30, 30, 30),):
assert calculate_slot(raw, step) == expected
