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https://issues.apache.org/jira/browse/BEAM-10824?focusedWorklogId=478023&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-478023
]
ASF GitHub Bot logged work on BEAM-10824:
-----------------------------------------
Author: ASF GitHub Bot
Created on: 02/Sep/20 18:08
Start Date: 02/Sep/20 18:08
Worklog Time Spent: 10m
Work Description: monicadsong commented on a change in pull request
#12756:
URL: https://github.com/apache/beam/pull/12756#discussion_r482266705
##########
File path: sdks/python/apache_beam/transforms/stats_test.py
##########
@@ -496,6 +483,51 @@ def
test_approximate_unique_globally_by_error_with_skewed_data(self):
equal_to([True]),
label='assert:globally_by_error_with_skewed_data')
+ def test_approximate_unique_combine_fn_by_nondeterministic_coder(self):
+ # test if the combiner throws an error with a nondeterministic coder.
+ sample_size = 30
+ coder = coders.Base64PickleCoder()
+
+ with self.assertRaises(ValueError) as e:
+ _ = ApproximateUniqueCombineFn(sample_size, coder)
+
+ self.assertRegex(
+ e.exception.args[0],
+ 'The key coder "Base64PickleCoder" '
+ 'for ApproximateUniqueCombineFn is not deterministic.')
+
+ def test_approximate_unique_combine_fn_add_values(self):
Review comment:
done.
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Issue Time Tracking
-------------------
Worklog Id: (was: 478023)
Remaining Estimate: 19h 50m (was: 20h)
Time Spent: 4h 10m (was: 4h)
> Hash in stats.ApproximateUniqueCombineFn NON-deterministic
> ----------------------------------------------------------
>
> Key: BEAM-10824
> URL: https://issues.apache.org/jira/browse/BEAM-10824
> Project: Beam
> Issue Type: Bug
> Components: sdk-py-core
> Reporter: Monica Song
> Priority: P1
> Labels: hash
> Original Estimate: 24h
> Time Spent: 4h 10m
> Remaining Estimate: 19h 50m
>
> The python hash() function is non-deterministic. As a result, different
> workers will map identical values to different hashes. This leads to
> overestimation of the number of unique values (by several magnitudes, in my
> experience x1000) in a distributed processing model.
> [https://github.com/apache/beam/blob/master/sdks/python/apache_beam/transforms/stats.py#L218]
>
>
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