You are viewing a plain text version of this content. The canonical link for it is here.
Posted to issues@hive.apache.org by "Eugene Koifman (JIRA)" <ji...@apache.org> on 2018/02/22 17:23:00 UTC
[jira] [Updated] (HIVE-18747) Cleaner for TXN_TO_WRITE_ID table
entries/MIN_HISTORY_LEVEL.
[ https://issues.apache.org/jira/browse/HIVE-18747?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Eugene Koifman updated HIVE-18747:
----------------------------------
Summary: Cleaner for TXN_TO_WRITE_ID table entries/MIN_HISTORY_LEVEL. (was: Cleaner for TXN_TO_WRITE_ID table entries.)
> Cleaner for TXN_TO_WRITE_ID table entries/MIN_HISTORY_LEVEL.
> ------------------------------------------------------------
>
> Key: HIVE-18747
> URL: https://issues.apache.org/jira/browse/HIVE-18747
> Project: Hive
> Issue Type: Sub-task
> Components: Transactions
> Affects Versions: 3.0.0
> Reporter: Sankar Hariappan
> Assignee: Sankar Hariappan
> Priority: Minor
> Labels: ACID
> Fix For: 3.0.0
>
>
> Per table write ID implementation (HIVE-18192) maintains a map between txn ID and table write ID in TXN_TO_WRITE_ID meta table.
> The entries in this table is used to generate ValidWriteIdList for the given ValidTxnList to ensure snapshot isolation.
> When table or database is dropped, then these entries are cleaned-up. But, it is necessary to clean-up for active tables too for better performance.
> Need to have another table MIN_HISTORY_LEVEL to maintain the least txn which is referred by any active ValidTxnList snapshot as open/aborted txn. If no references found in this table for any txn, then it is eligible for cleanup.
> After clean-up, need to maintain just one entry per table to mark as LWM (low water mark).
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)