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Posted to issues@hive.apache.org by "Sankar Hariappan (JIRA)" <ji...@apache.org> on 2018/03/09 08:38:00 UTC
[jira] [Assigned] (HIVE-18923) ValidWriteIdList snapshot per table
can be cached for multi-statement transactions.
[ https://issues.apache.org/jira/browse/HIVE-18923?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Sankar Hariappan reassigned HIVE-18923:
---------------------------------------
> ValidWriteIdList snapshot per table can be cached for multi-statement transactions.
> -----------------------------------------------------------------------------------
>
> Key: HIVE-18923
> URL: https://issues.apache.org/jira/browse/HIVE-18923
> 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
>
>
> Currently, for each query within a multi-statement transaction, it would request metastore/TxnHandler to build ValidWriteIdList snapshot for the given table. But, the snapshot won't change within the duration of transaction. So, it make sense to cache it within QueryTxnManager.
> However, each txn should be able to view their own written rows. So, when a transaction allocates writeId to write on a table, then the cached ValidWriteIdList on this table should be recalculated as follows.
> Original ValidWriteIdList: \{hwm=10, open/aborted=5,6} – (10 is allocated by txn < current txn_id).
> Allocated writeId for this txn: 13 – (11 and 12 are taken by some other txn > current txn_id)
> New ValidWriteIdList: \{hwm=12, open/aborted=5,6,11, 12} – (11, 12 are added to invalid list, so the snapshot remains same).
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