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Posted to issues@hive.apache.org by "Janaki Lahorani (JIRA)" <ji...@apache.org> on 2018/06/14 00:06:00 UTC
[jira] [Assigned] (HIVE-19889) Wrong results due to PPD of non
deterministic functions with CBO
[ https://issues.apache.org/jira/browse/HIVE-19889?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Janaki Lahorani reassigned HIVE-19889:
--------------------------------------
> Wrong results due to PPD of non deterministic functions with CBO
> ----------------------------------------------------------------
>
> Key: HIVE-19889
> URL: https://issues.apache.org/jira/browse/HIVE-19889
> Project: Hive
> Issue Type: Bug
> Reporter: Janaki Lahorani
> Assignee: Janaki Lahorani
> Priority: Major
>
> The following query can give wrong results when CBO is on:
> select * from (
> select part1,randum123
> from (SELECT *, cast(rand() as double) AS randum123 FROM testA where part1='CA' and part2 = 'ABC') a
> where randum123 <= 0.5) s where s.randum123 > 0.25 limit 20;
> The plan of the query is as follows:
> STAGE PLANS:
> Stage: Stage-1
> Map Reduce
> Map Operator Tree:
> TableScan
> alias: testa
> Statistics: Num rows: 2 Data size: 4580 Basic stats: COMPLETE Column stats: NONE
> Filter Operator
> predicate: ((rand() <= 0.5D) and (rand() > 0.25D)) (type: boolean)
> Statistics: Num rows: 1 Data size: 2290 Basic stats: COMPLETE Column stats: NONE
> Select Operator
> expressions: 'CA' (type: string), rand() (type: double)
> outputColumnNames: _col0, _col1
> Statistics: Num rows: 1 Data size: 2290 Basic stats: COMPLETE Column stats: NONE
> Limit
> Number of rows: 20
> Statistics: Num rows: 1 Data size: 2290 Basic stats: COMPLETE Column stats: NONE
> File Output Operator
> compressed: false
> Statistics: Num rows: 1 Data size: 2290 Basic stats: COMPLETE Column stats: NONE
> table:
> input format: org.apache.hadoop.mapred.SequenceFileInputFormat
> output format: org.apache.hadoop.hive.ql.io.HiveSequenceFileOutputFormat
> serde: org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe
> Stage: Stage-0
> Fetch Operator
> limit: 20
> Processor Tree:
> ListSink
> The relevant part in the plan is the filter:
> Filter Operator
> predicate: ((rand() <= 0.5D) and (rand() > 0.25D)) (type: boolean)
> The predicates s.randum123 > 0.25 and s.randum123 > 0.25 were pushed down. And randum123 was resolved to rand(). This is bad because it will result in invocation of rand() two times and rand() UDF is non-deterministic. Both the rand calls can generate values that can satisfy the predicates independently, but not together, whereas the original intention of the query is to give results when rand falls between 0.25 and 0.5.
> A sample result:
> CA 0.9191984370369802
> CA 0.397933021566812
> where the condition was not satisfied.
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