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

Reply via email to