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shunping merged 3 commits into from
Oct 29, 2025
Merged

Ensure consistent behavior between streaming and batch order window elements #36661

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c372dbe
Make the behavior of streaming order window elements similar to the b…
shunping Oct 29, 2025
2a8a57a
Fix lints.
shunping Oct 29, 2025
f917832
Revise code according to review.
shunping Oct 29, 2025
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39 changes: 26 additions & 13 deletions sdks/python/apache_beam/examples/cookbook/ordered_window_elements/streaming.py
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,7 @@
from apache_beam.typehints.typehints import TupleConstraint
from apache_beam.utils.timestamp import MAX_TIMESTAMP
from apache_beam.utils.timestamp import MIN_TIMESTAMP
from apache_beam.utils.timestamp import Duration
from apache_beam.utils.timestamp import DurationTypes # pylint: disable=unused-import
from apache_beam.utils.timestamp import Timestamp
from apache_beam.utils.timestamp import TimestampTypes # pylint: disable=unused-import
Expand Down Expand Up @@ -89,7 +90,7 @@ def __init__(
self,
duration: DurationTypes,
slide_interval: DurationTypes,
offset: TimestampTypes,
offset: DurationTypes,
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@liferoad liferoad Oct 29, 2025 •
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looks like a break change to me. Could we keep both like offset: Union[TimestampTypes, DurationTypes]?

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@shunping shunping Oct 29, 2025

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The transform is part of an example, so it won't matter if it is a breaking change.

This is to fix the offset type, as it should be a Duration.

allowed_lateness: DurationTypes,
default_start_value,
fill_start_if_missing: bool,
Expand Down Expand Up @@ -200,11 +201,23 @@ def process(

timer_started = timer_state.read()
if not timer_started:
offset_duration = Duration.of(self.offset)
slide_duration = Duration.of(self.slide_interval)
duration_duration = Duration.of(self.duration)

# Align the timestamp with the windowing scheme.
aligned_micros = (timestamp - offset_duration).micros

# Calculate the start of the last window that could contain this timestamp
last_window_start_aligned_micros = (
(aligned_micros // slide_duration.micros) * slide_duration.micros)

last_window_start = Timestamp(
micros=last_window_start_aligned_micros) + offset_duration
n = (duration_duration.micros - 1) // slide_duration.micros
# Calculate the start of the first sliding window.
first_slide_start = int(
(timestamp.micros / 1e6 - self.offset) //
self.slide_interval) * self.slide_interval + self.offset
first_slide_start_ts = Timestamp.of(first_slide_start)
first_slide_start_ts = last_window_start - Duration(
micros=n * slide_duration.micros)

# Set the initial timer to fire at the end of the first window plus
# allowed lateness.
Expand Down Expand Up @@ -256,14 +269,16 @@ def _get_windowed_values_from_state(
if not windowed_values:
# If the window is empty, use the last value.
last_value = last_value_state.read()
windowed_values.append(last_value)
value_to_insert = (window_start_ts, last_value[1])
windowed_values.append(value_to_insert)
else:
first_timestamp = windowed_values[0][0]
last_value = last_value_state.read()
if first_timestamp > window_start_ts and last_value:
# Prepend the last value if there's a gap between the first element
# in the window and the start of the window.
windowed_values = [last_value] + windowed_values
value_to_insert = (window_start_ts, last_value[1])
windowed_values = [value_to_insert] + windowed_values

# Find the last element before the beginning of the next window to update
# last_value_state.
Expand Down Expand Up @@ -334,8 +349,7 @@ def on_timer(
windowed_values = self._get_windowed_values_from_state(
buffer_state, late_start_ts, late_end_ts, last_value_state)
yield TimestampedValue(
((key, late_start_ts, late_end_ts), [v[1]
for v in windowed_values]),
(key, ((late_start_ts, late_end_ts), windowed_values)),
late_end_ts - 1)
late_start_ts += self.slide_interval

Expand All @@ -347,8 +361,7 @@ def on_timer(
windowed_values = self._get_windowed_values_from_state(
buffer_state, window_start_ts, window_end_ts, last_value_state)
yield TimestampedValue(
((key, window_start_ts, window_end_ts), [v[1]
for v in windowed_values]),
(key, ((window_start_ts, window_end_ts), windowed_values)),
window_end_ts - 1)

# Post-emit actions for the current window:
Expand Down Expand Up @@ -532,7 +545,7 @@ def __init__(
self,
duration: DurationTypes,
slide_interval: Optional[DurationTypes] = None,
offset: TimestampTypes = 0,
offset: DurationTypes = 0,
allowed_lateness: DurationTypes = 0,
default_start_value=None,
fill_start_if_missing: bool = False,
Expand Down Expand Up @@ -617,7 +630,7 @@ def expand(self, input):
self.stop_timestamp)))

if isinstance(input.element_type, TupleConstraint):
ret = keyed_output | beam.MapTuple(lambda x, y: (x[0], y))
ret = keyed_output
else:
# Remove the default key if the input PCollection was originally unkeyed.
ret = keyed_output | beam.Values()
Expand Down
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