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https://issues.apache.org/jira/browse/IMPALA-12588?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Noémi Pap-Takács resolved IMPALA-12588.
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Resolution: Fixed
> Don't update rows that already have the desired value
> -----------------------------------------------------
>
> Key: IMPALA-12588
> URL: https://issues.apache.org/jira/browse/IMPALA-12588
> Project: IMPALA
> Issue Type: Improvement
> Components: Frontend
> Reporter: Zoltán Borók-Nagy
> Assignee: Noémi Pap-Takács
> Priority: Major
> Labels: impala-iceberg
>
> When UPDATEing an Iceberg table, we should write as few new data records and
> delete records as possible.
> Therefore, if rows already have the new values we should just ignore them.
> One way to achieve this is to add extra predicates, e.g.:
> {noformat}
> UPDATE tbl SET k = 3 WHERE i > 4;
> ==>
> UPDATE tbl SET k = 3 WHERE i > 4 AND k != 3;
> {noformat}
> So we won't write new data/delete records for the rows that already have the
> desired value.
> For some cases in can be trickier (e.g. UPDATE FROM), those cases could be
> handled more easily by the new MERGE statement when we have it.
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