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https://issues.apache.org/jira/browse/BEAM-6695?focusedWorklogId=224758&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-224758
]
ASF GitHub Bot logged work on BEAM-6695:
----------------------------------------
Author: ASF GitHub Bot
Created on: 09/Apr/19 03:05
Start Date: 09/Apr/19 03:05
Worklog Time Spent: 10m
Work Description: ttanay commented on pull request #8206: [BEAM-6695]
Latest PTransform for Python SDK
URL: https://github.com/apache/beam/pull/8206#discussion_r273310080
##########
File path: sdks/python/apache_beam/transforms/combiners.py
##########
@@ -858,3 +860,60 @@ def merge_only(self, accumulators):
def extract_only(self, accumulator):
return self.combine_fn.extract_output(accumulator)
+
+
+class Latest(object):
+ """Combiners for computing the latest element"""
+
+ class Globally(ptransform.PTransform):
+ """Compute the element with the latest timestamp from a
+ PCollection."""
+
+ @staticmethod
+ def add_timestamp(element, timestamp=core.DoFn.TimestampParam):
+ return [(element, timestamp)]
+
+ def expand(self, pcoll):
+ return (pcoll
+ | core.ParDo(self.add_timestamp)
+ | core.CombineGlobally(LatestCombineFn()))
+
+ class PerKey(ptransform.PTransform):
+ """Compute elements with the latest timestamp for each key
+ from a keyed PCollection"""
+
+ @staticmethod
+ def add_timestamp(element, timestamp=core.DoFn.TimestampParam):
+ _check_instance_type(KV[T, T], element)
+ (K, V) = element
+ return [(K, (V, timestamp))]
+
+ def expand(self, pcoll):
+ return (pcoll
+ | core.ParDo(self.add_timestamp)
+ | core.CombinePerKey(LatestCombineFn()))
+
+
+@with_input_types(KV[T, T])
Review comment:
I agree. It should be a Tuple rather than a KV.
Also, only types int, float, long, Timestamp and Duration can be interpreted
as timestamps[1] so they can be compared to `window.MIN_TIMESTAMP` in the
accumulator. So, having the timestamp's type as T would be less restrictive.
Does it make sense to create a new type - `TimestampT/TimestampType =
Union[int, float, long, Timestamp, Duration]` in typehints.py or the combiners
module? This would make the input type `Tuple[T, TimestampType]`.
[1]
https://github.com/apache/beam/blob/master/sdks/python/apache_beam/utils/timestamp.py#L71
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Issue Time Tracking
-------------------
Worklog Id: (was: 224758)
Time Spent: 4h 40m (was: 4.5h)
> Latest transform for Python SDK
> -------------------------------
>
> Key: BEAM-6695
> URL: https://issues.apache.org/jira/browse/BEAM-6695
> Project: Beam
> Issue Type: New Feature
> Components: sdk-py-core
> Reporter: Ahmet Altay
> Assignee: Tanay Tummalapalli
> Priority: Minor
> Time Spent: 4h 40m
> Remaining Estimate: 0h
>
> Add a PTransform} and Combine.CombineFn for computing the latest element in a
> PCollection.
> It should offer the same API as its Java counterpart:
> https://github.com/apache/beam/blob/11a977b8b26eff2274d706541127c19dc93131a2/sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/Latest.java
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