Grokbase Groups Hive user August 2010
FAQ
The idea is that in a large shared cluster, you can use this to protect "important" tables from accidents. This includes protection from bugs in non-human agents such as automated retention/cleanup processes, which are likely to run as an account with full privileges.

For tables which are temporary, unimportant, short-lived, or still under development, you wouldn't bother protecting them.

JVS

On Aug 4, 2010, at 2:19 PM, Bakshi, Ankita wrote:

Thanks John for an interesting analogy.
Can you pls. also elaborate the use case for this feature? It seems that after this feature, the best practice would be to always keep no_drop mode ON to avoid accidental drop even by the creator.

Ankita

________________________________
From: John Sichi
Sent: Wednesday, August 04, 2010 11:15 AM
To: <hive-user@hadoop.apache.org
Subject: Re: how to prevent user from dropping table created by another user

Slight clarification: the no_drop support Siying is adding will apply to all users (even the creator of the table).

The analogy is as follows: no_drop mode is like the safety catch on a gun (it prevents the gun from being fired by anyone, even the person holding it, until explicitly taken off), whereas HDFS or other permission is like the key to the gun cabinet.

JVS

On Aug 4, 2010, at 10:36 AM, Ning Zhang wrote:


Siying is working on a JIRA (HIVE-1413) addressing exactly the issue (non-dropable tables).

On Aug 4, 2010, at 10:25 AM, Bakshi, Ankita wrote:



Thanks Carl for the pointers.
Good news is - user can recover from the failure by doing following steps:
1. For tables without partition, it is as simple as creating table definition again.
2. For tables with partition, it will involve creating table definition followed by creating partitions.

Thanks,
Ankita

________________________________
From: Carl Steinbach
Sent: Tuesday, August 03, 2010 4:17 PM
To: hive-user@hadoop.apache.org
Subject: Re: how to prevent user from dropping table created by another user

Hi Ankita,
We wanted to avoid user from dropping table created by another user. By changing the hdfs permission of the table dir, we were able to prevent the table from getting deleted from hdfs. But unfortunately, hive deletes the metadata related to the table from the mysql metastore.

The strategy that Hive currently employs for operations like this is to first attempt update the data in the metastore db, and iff that succeeds it then attempts to make the corresponding changes in HDFS. Eventually we hope to build authorization facilities into the MetaStore (see https://issues.apache.org/jira/browse/HIVE-78).

I am wondering if any one has any pointers to this problem.
It would also help if someone could point me to the hive code where it is doing deletion. It seems that we just have to exit if hdfs throws error and should not delete metadata in this case.

The code you're looking for is the drop_table_core() method in metastore/src/java/org/apache/hadoop/hive/metastore/HiveMetaStore.java.

Thanks.

Carl


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