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https://issues.apache.org/jira/browse/SPARK-14393?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15884486#comment-15884486
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Everett Anderson commented on SPARK-14393:
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Appears this also happens in 2.0.2.
Thanks for fixing this!
I disagree that monotonically_increasing_id function should ever be allowed to
create duplicate values in a table given its documentation is "The generated ID
is guaranteed to be monotonically increasing and unique, but not consecutive."
We were certainly relying on it to produce unique values!
> values generated by non-deterministic functions shouldn't change after
> coalesce or union
> ----------------------------------------------------------------------------------------
>
> Key: SPARK-14393
> URL: https://issues.apache.org/jira/browse/SPARK-14393
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 1.6.0, 2.0.0, 2.0.1
> Reporter: Jason Piper
> Assignee: Xiangrui Meng
> Priority: Blocker
> Labels: correctness, releasenotes
> Fix For: 2.1.0
>
>
> When utilising monotonicallyIncreasingId with a coalesce, it appears that
> every partition uses the same offset (0) leading to non-monotonically
> increasing IDs.
> See examples below
> {code}
> >>> sqlContext.range(10).select(monotonicallyIncreasingId()).show()
> +---------------------------+
> |monotonicallyincreasingid()|
> +---------------------------+
> | 25769803776|
> | 51539607552|
> | 77309411328|
> | 103079215104|
> | 128849018880|
> | 163208757248|
> | 188978561024|
> | 214748364800|
> | 240518168576|
> | 266287972352|
> +---------------------------+
> >>> sqlContext.range(10).select(monotonicallyIncreasingId()).coalesce(1).show()
> +---------------------------+
> |monotonicallyincreasingid()|
> +---------------------------+
> | 0|
> | 0|
> | 0|
> | 0|
> | 0|
> | 0|
> | 0|
> | 0|
> | 0|
> | 0|
> +---------------------------+
> >>> sqlContext.range(10).repartition(5).select(monotonicallyIncreasingId()).coalesce(1).show()
> +---------------------------+
> |monotonicallyincreasingid()|
> +---------------------------+
> | 0|
> | 1|
> | 0|
> | 0|
> | 1|
> | 2|
> | 3|
> | 0|
> | 1|
> | 2|
> +---------------------------+
> {code}
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