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Posted to issues-all@impala.apache.org by "Balazs Jeszenszky (JIRA)" <ji...@apache.org> on 2018/09/05 09:38:00 UTC
[jira] [Updated] (IMPALA-7528) Division by zero when computing
cardinalities of many to many joins on NULL columns
[ https://issues.apache.org/jira/browse/IMPALA-7528?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Balazs Jeszenszky updated IMPALA-7528:
--------------------------------------
Issue Type: Bug (was: Improvement)
> Division by zero when computing cardinalities of many to many joins on NULL columns
> -----------------------------------------------------------------------------------
>
> Key: IMPALA-7528
> URL: https://issues.apache.org/jira/browse/IMPALA-7528
> Project: IMPALA
> Issue Type: Bug
> Components: Frontend
> Affects Versions: Impala 2.12.0
> Reporter: Balazs Jeszenszky
> Priority: Major
>
> The following:
> {code:java}
> | F00:PLAN FRAGMENT [RANDOM] hosts=1 instances=1 |
> | Per-Host Resources: mem-estimate=33.94MB mem-reservation=1.94MB |
> | 02:HASH JOIN [INNER JOIN, BROADCAST] |
> | | hash predicates: b.code = a.code |
> | | fk/pk conjuncts: none |
> | | runtime filters: RF000 <- a.code |
> | | mem-estimate=1.94MB mem-reservation=1.94MB spill-buffer=64.00KB |
> | | tuple-ids=1,0 row-size=163B cardinality=9223372036854775807 |
> | | |
> | |--03:EXCHANGE [BROADCAST] |
> | | | mem-estimate=0B mem-reservation=0B |
> | | | tuple-ids=0 row-size=82B cardinality=823 |
> | | | |
> | | F01:PLAN FRAGMENT [RANDOM] hosts=1 instances=1 |
> | | Per-Host Resources: mem-estimate=32.00MB mem-reservation=0B |
> | | 00:SCAN HDFS [default.sample_07 a, RANDOM] |
> | | partitions=1/1 files=1 size=44.98KB |
> | | stats-rows=823 extrapolated-rows=disabled |
> | | table stats: rows=823 size=44.98KB |
> | | column stats: all |
> | | mem-estimate=32.00MB mem-reservation=0B |
> | | tuple-ids=0 row-size=82B cardinality=823 |
> | | |
> | 01:SCAN HDFS [default.sample_08 b, RANDOM] |
> | partitions=1/1 files=1 size=44.99KB |
> | runtime filters: RF000 -> b.code |
> | stats-rows=823 extrapolated-rows=disabled |
> | table stats: rows=823 size=44.99KB |
> | column stats: all |
> | mem-estimate=32.00MB mem-reservation=0B |
> | tuple-ids=1 row-size=82B cardinality=823 |
> +--------------------------------------------------------------------+
> {code}
> is the result of both join columns having 0 as NDV.
> https://github.com/cloudera/Impala/blob/cdh5-trunk/fe/src/main/java/org/apache/impala/planner/JoinNode.java#L368
> should handle a potential division by zero.
> IMPALA-7310 makes it a bit more likely that someone will run into this.
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