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From "Denys Kuzmenko (Jira)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-23042) Merge queries to a single one for updating MIN_OPEN_TXNS table
Date Fri, 20 Mar 2020 14:16:00 GMT

    [ https://issues.apache.org/jira/browse/HIVE-23042?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17063399#comment-17063399
] 

Denys Kuzmenko commented on HIVE-23042:
---------------------------------------

+1

> Merge queries to a single one for updating MIN_OPEN_TXNS table
> --------------------------------------------------------------
>
>                 Key: HIVE-23042
>                 URL: https://issues.apache.org/jira/browse/HIVE-23042
>             Project: Hive
>          Issue Type: Bug
>          Components: Transactions
>            Reporter: Peter Vary
>            Assignee: Peter Vary
>            Priority: Major
>         Attachments: HIVE-23042.2.patch, HIVE-23042.3.patch, HIVE-23042.4.patch, HIVE-23042.patch
>
>
> When opening a new transaction we issue 2 queries to update the MIN_OPEN_TXN table.
> {code}
> <SELECT MIN("TXN_ID") FROM "TXNS" WHERE "TXN_STATE" = 'o'>
> <insert into "MIN_HISTORY_LEVEL" ("MHL_TXNID", "MHL_MIN_OPEN_TXNID") values(763, 763)>
> {code}
> This could be archived with a single query faster, if we do not open transactions in
batch, like:
> {code}
> <INSERT INTO "MIN_HISTORY_LEVEL" ("MHL_TXNID", "MHL_MIN_OPEN_TXNID")
>   SELECT ?, MIN("TXN_ID") FROM "TXNS" WHERE "TXN_STATE" = 'o'>
> {code}



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