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Posted to issues-all@impala.apache.org by "ASF subversion and git services (JIRA)" <ji...@apache.org> on 2019/08/11 02:19:00 UTC
[jira] [Commented] (IMPALA-8848) Cardinality of UnionNode does not
handle missing input cardinality correctly
[ https://issues.apache.org/jira/browse/IMPALA-8848?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16904541#comment-16904541 ]
ASF subversion and git services commented on IMPALA-8848:
---------------------------------------------------------
Commit 2066b72bc4b43fd57679c37145eecebaa6be8b27 in impala's branch refs/heads/master from Tim Armstrong
[ https://gitbox.apache.org/repos/asf?p=impala.git;h=2066b72 ]
IMPALA-8848: fix UNION missing input cardinality bug
If a UNION has children, and none of those children has
a known cardinality, then we can make no reasonable
estimate of the output cardinality, so the planner
should consider the output cardinality to be unknown.
The previous behaviour was to report a cardinality of
0, which is unsafe because the planner may make further
decisions under the incorrect assumption that the output
of the UNION is tiny.
Testing:
An existing CardinalityTest already tested this but had
the wrong estimate.
Change-Id: Ic3ed670ffb685d8ff24824933ca303f3219737bb
Reviewed-on: http://gerrit.cloudera.org:8080/14036
Reviewed-by: Impala Public Jenkins <im...@cloudera.com>
Tested-by: Impala Public Jenkins <im...@cloudera.com>
> Cardinality of UnionNode does not handle missing input cardinality correctly
> ----------------------------------------------------------------------------
>
> Key: IMPALA-8848
> URL: https://issues.apache.org/jira/browse/IMPALA-8848
> Project: IMPALA
> Issue Type: Bug
> Components: Frontend
> Affects Versions: Impala 3.3.0
> Reporter: Tim Armstrong
> Assignee: Tim Armstrong
> Priority: Critical
> Labels: planner
> Attachments: profile_4d48b2a3bb0236f1_bfa8157d00000000
>
>
> {noformat}
> | 35:UNION
> | | mem-estimate=0B mem-reservation=0B thread-reservation=0
> | | tuple-ids=82 row-size=28B cardinality=0
> | | in pipelines: 75(GETNEXT)
> | |
> | 75:AGGREGATE [FINALIZE]
> | | output: sum:merge((((ws_ext_list_price - ws_ext_wholesale_cost - ws_ext_discount_amt) + ws_ext_sales_price) / 2))
> | | group by: c_customer_id, c_first_name, c_last_name, c_preferred_cust_flag, c_birth_country, c_login, c_email_address, d_year
> | | mem-estimate=128.00MB mem-reservation=34.00MB spill-buffer=2.00MB thread-reservation=0
> | | tuple-ids=81 row-size=104B cardinality=unavailable
> | | in pipelines: 75(GETNEXT), 36(OPEN)
> {noformat}
> I expect that the cardinality should be unavailable, not 0.
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