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https://issues.apache.org/jira/browse/HIVE-18825?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16382598#comment-16382598
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Jesus Camacho Rodriguez commented on HIVE-18825:
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[~ekoifman], thanks. It is not about opening the txn after I get the list, the
call to get the valid txn list happens after we might open a transaction in
Driver#compile (L595) (I have not changed that).
We hit the assertion when we have not open a transaction yet at all (for
instance, first line to execute in the test is 'use databasex;'). For safety, I
can keep the assertion, and only create the valid txn list if we have already
opened a transaction in the system. Does it sound reasonable?
> 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.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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