[ 
https://issues.apache.org/jira/browse/HIVE-20890?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
 ]

Denys Kuzmenko updated HIVE-20890:
----------------------------------
    Attachment: HIVE-20890.2.patch

> ACID: Allow whole table ReadLocks to skip all partition locks
> -------------------------------------------------------------
>
>                 Key: HIVE-20890
>                 URL: https://issues.apache.org/jira/browse/HIVE-20890
>             Project: Hive
>          Issue Type: Improvement
>          Components: Transactions
>            Reporter: Gopal Vijayaraghavan
>            Assignee: Denys Kuzmenko
>            Priority: Major
>         Attachments: HIVE-20890.1.patch, HIVE-20890.2.patch
>
>
> HIVE-19369 proposes adding a EXCL_WRITE lock which does not wait for any 
> SHARED_READ locks for read operations - in the presence of that lock, the 
> insert overwrite no longer takes an exclusive lock.
> The only exclusive operation will be a schema change or drop table, which 
> should take an exclusive lock on the entire table directly.
> {code}
> explain locks select * from tpcds_bin_partitioned_orc_1000.store_sales where 
> ss_sold_date_sk=2452626 
> +----------------------------------------------------+
> |                      Explain                       |
> +----------------------------------------------------+
> | LOCK INFORMATION:                                  |
> | tpcds_bin_partitioned_orc_1000.store_sales -> SHARED_READ |
> | tpcds_bin_partitioned_orc_1000.store_sales.ss_sold_date_sk=2452626 -> 
> SHARED_READ |
> +----------------------------------------------------+
> {code}
> So the per-partition SHARED_READ locks are no longer necessary, if the lock 
> builder already includes the table-wide SHARED_READ locks.
> The removal of entire partitions is the only part which needs to be taken 
> care of within this semantics as row-removal instead of directory removal 
> (i.e "drop partition" -> "truncate partition" and have the truncation trigger 
> a whole directory cleaner, so that the partition disappears when there are 0 
> rows left).



--
This message was sent by Atlassian Jira
(v8.3.4#803005)

Reply via email to