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https://issues.apache.org/jira/browse/HIVE-24632?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17266037#comment-17266037
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Zhihua Deng commented on HIVE-24632:
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Thanks a lot for the merge and review, [~kgyrtkirk]!
> Replace with null when GenericUDFBaseCompare has a non-interpretable val
> ------------------------------------------------------------------------
>
> Key: HIVE-24632
> URL: https://issues.apache.org/jira/browse/HIVE-24632
> Project: Hive
> Issue Type: Improvement
> Components: Parser
> Affects Versions: 4.0.0
> Reporter: Zhihua Deng
> Priority: Major
> Labels: pull-request-available
> Fix For: 4.0.0
>
> Time Spent: 50m
> Remaining Estimate: 0h
>
> The query
> {code:java}
> create table ccn_table(key int, value string);
> set hive.cbo.enable=false;
> select * from ccn_table where key > '123a' ;
> {code}
> will scan all records(partitions) compared to older version, as the plan
> tells:
> {noformat}
> STAGE PLANS:
> Stage: Stage-0
> Fetch Operator
> limit: -1
> Processor Tree:
> TableScan
> alias: ccn_table
> filterExpr: (key > '123a') (type: boolean)
> Statistics: Num rows: 2 Data size: 180 Basic stats: COMPLETE Column
> stats: COMPLETE
> GatherStats: false
> Filter Operator
> isSamplingPred: false
> predicate: (key > '123a') (type: boolean)
> Statistics: Num rows: 1 Data size: 90 Basic stats: COMPLETE Column
> stats: COMPLETE
> Select Operator
> expressions: key (type: int), value (type: string)
> outputColumnNames: _col0, _col1
> Statistics: Num rows: 1 Data size: 90 Basic stats: COMPLETE
> Column stats: COMPLETE
> ListSink{noformat}
> When the TypeCheckProcFactory#getXpathOrFuncExprNodeDesc validates the expr:
> +key > '123a',+ the operator(>) is not an equal operator(=), so the factory
> returns +key > '123a'+ as it is. However all the subclass of
> GenericUDFBaseCompare(except GenericUDFOPEqualNS and GenericUDFOPNotEqualNS)
> would return null if either side of the function children is null, so it's
> safe to return constant null when processing the expr +`key > '123a'`+. This
> will benifit some queries when the cbo is disabled.
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