[jira] [Updated] (IMPALA-12588) Don't update rows that already have the desired value

["Noemi Pap-Takacs (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IMPALA-12588?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Noemi Pap-Takacs updated IMPALA-12588:
--------------------------------------
    Issue Type: Improvement  (was: Bug)

> 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: Noemi Pap-Takacs
>            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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