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From "Gopal V (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HIVE-20890) ACID: Allow whole table ReadLocks to skip all partition locks
Date Thu, 08 Nov 2018 07:05:00 GMT

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

Gopal V updated HIVE-20890:
---------------------------
    Issue Type: Improvement  (was: Bug)

> 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 V
>            Priority: Major
>
> HIVE-19369 proposes adding a EXCL_WRITE lock which does not wait for any SHARED_READ
locks for insert 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).



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