Sankar Hariappan commented on HIVE-18864:


That is precisely the problem here. 

write_HWM=7, corresponds to txn_HWM=10. But, the sequence of allocating write 
ID is that txn=11 gets writeId=6 and txn=10 gets writeId=7 which expects, 
writeId=6 should be added to invalid/open list.

> WriteId high water mark (HWM) is incorrect if ValidWriteIdList is obtained 
> after allocating writeId by current transaction.
> ---------------------------------------------------------------------------------------------------------------------------
>                 Key: HIVE-18864
>                 URL: https://issues.apache.org/jira/browse/HIVE-18864
>             Project: Hive
>          Issue Type: Sub-task
>          Components: Transactions
>    Affects Versions: 3.0.0
>            Reporter: Sankar Hariappan
>            Assignee: Sankar Hariappan
>            Priority: Major
>              Labels: ACID
>             Fix For: 3.0.0
> For multi-statement txns, it is possible that write on a table happens after 
> a read. Let's see the below scenario.
>  # Committed txn=9 writes on table T1 with writeId=5.
>  # Open txn=10. ValidTxnList(open:null, txn_HWM=10),
>  # Read table T1 from txn=10. ValidWriteIdList(open:null, write_HWM=5).
>  # Open txn=11, writes on table T1 with writeid=6.
>  # Read table T1 from txn=10. ValidWriteIdList(open:null, write_HWM=5).
>  # Write table T1 from txn=10 with writeId=7.
>  # Read table T1 from txn=10. {color:#d04437}*ValidWriteIdList(open:null, 
> write_HWM=7)*. – This read will able to see rows added by txn=11 which is 
> still open.{color}
> {color:#d04437}So, it is needed to rebuild the open/aborted list of 
> ValidWriteIdList based on txn_HWM. Any writeId allocated by txnId > txn_HWM 
> should be marked as open.{color}
> {color:#333333}{color:#d04437}cc{color}{color} 
> [~ekoifman]{color:#333333},{color} [~thejas]

This message was sent by Atlassian JIRA

Reply via email to