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https://issues.apache.org/jira/browse/HIVE-18825?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16388925#comment-16388925
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Eugene Koifman commented on HIVE-18825:
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I'm strongly against this.

> Define ValidTxnList before starting query optimization
> ------------------------------------------------------
>
>                 Key: HIVE-18825
>                 URL: https://issues.apache.org/jira/browse/HIVE-18825
>             Project: Hive
>          Issue Type: Improvement
>          Components: Transactions
>    Affects Versions: 3.0.0
>            Reporter: Jesus Camacho Rodriguez
>            Assignee: Jesus Camacho Rodriguez
>            Priority: Major
>         Attachments: HIVE-18825.01.patch, HIVE-18825.02.patch, 
> HIVE-18825.03.patch, HIVE-18825.04.patch, HIVE-18825.patch
>
>
> Consider a set of tables used by a materialized view where inserts happened 
> after the materialization was created. To compute incremental view 
> maintenance, we need to be able to filter only new rows from those base 
> tables. That can be done by inserting a filter operator with condition e.g. 
> {{ROW\_\_ID.transactionId < highwatermark and ROW\_\_ID.transactionId NOT 
> IN(<open txns>)}} on top of the MVs query definition and triggering the 
> rewriting (which should in turn produce a partial rewriting). However, to do 
> that, we need to have a value for {{ValidTxnList}} during query compilation 
> so we know the snapshot that we are querying.
> This patch aims to generate {{ValidTxnList}} before query optimization. There 
> should not be any visible changes for end user.



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