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https://issues.apache.org/jira/browse/BEAM-3736?focusedWorklogId=499429&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-499429
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ASF GitHub Bot logged work on BEAM-3736:
----------------------------------------
Author: ASF GitHub Bot
Created on: 12/Oct/20 14:26
Start Date: 12/Oct/20 14:26
Worklog Time Spent: 10m
Work Description: kamilwu commented on a change in pull request #13048:
URL: https://github.com/apache/beam/pull/13048#discussion_r503332709
##########
File path: sdks/python/apache_beam/transforms/core.py
##########
@@ -1970,10 +1985,14 @@ def add_input_types(transform):
return combined
if self.has_defaults:
- combine_fn = (
- self.fn if isinstance(self.fn, CombineFn) else
- CombineFn.from_callable(self.fn))
- default_value = combine_fn.apply([], *self.args, **self.kwargs)
+ combine_fn = copy.copy(
Review comment:
Better protection against potential side effects.
If using default values, `CombineFn.apply` is called at pipeline
construction time. `CombineFn.setup` and `CombineFn.teardown` are called along
with it. The same instance of CombineFn is then serialized and sent to runner.
I think it would be better to perform initial `CombineFn.apply` on a copy, so
that the state of the instance is not polluted.
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Issue Time Tracking
-------------------
Worklog Id: (was: 499429)
Time Spent: 3h 50m (was: 3h 40m)
> Add SetUp() and TearDown() for CombineFns
> -----------------------------------------
>
> Key: BEAM-3736
> URL: https://issues.apache.org/jira/browse/BEAM-3736
> Project: Beam
> Issue Type: Improvement
> Components: beam-model, sdk-py-core
> Reporter: Chuan Yu Foo
> Assignee: Kamil Wasilewski
> Priority: P3
> Time Spent: 3h 50m
> Remaining Estimate: 0h
>
> I have a CombineFn that has a large amount of state that needs to be loaded
> once before it can add_input or merge_combiners (for example, the CombineFn
> might load up a large lookup table used for combining).
> Right now, to initialise this state, for each of the methods, I check if the
> state has already been initialised, and if not, I initialise it. It would be
> nice if CombineFn provided a SetUp() method that is called once to initialise
> this state (and a corresponding TearDown() method to clean up this state if
> necessary).
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