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From "Ashish Thusoo (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-788) Triggers when a new partition is created for a table
Date Tue, 25 Aug 2009 01:47:59 GMT

    [ https://issues.apache.org/jira/browse/HIVE-788?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12747177#action_12747177
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Ashish Thusoo commented on HIVE-788:
------------------------------------

The idea here is similar to DML triggers. If we do this as triggers on the insert and load
statements then we can address Edward's use case as well. Basically whenever data is added
to a table a trigger gets executed. Look at DML triggers at

Look at

http://dev.mysql.com/doc/refman/5.1/en/trigger-syntax.html

The DML triggers may be before or after inserts. You can find similar examples with Oracle.

One variation is obviously to execute a user script when the trigger fires.

A is better if the number of such scripts is low in number but if more and more users use
these mechanisms it become quickly non performant and would put a lot of load on the metastore.
Traditionally B has been the model is most RDBMSs so when we call these triggers users would
expect similar functionality perhaps.


> Triggers when a new partition is created for a table
> ----------------------------------------------------
>
>                 Key: HIVE-788
>                 URL: https://issues.apache.org/jira/browse/HIVE-788
>             Project: Hadoop Hive
>          Issue Type: New Feature
>            Reporter: Zheng Shao
>
> One requirement for HIVE-787 is that users would like to run a command whenever a new
partition of a Hive table gets created.
> There are several ways to achieve this functionality:
> A. Probe and wait: We can have the scripts running in a loop checking if a new partition
is created.
>   Pros: easy to write, easy to control
>   Cons: will introduce another delay based on the probing interval.
> B. Triggered: The command is registered inside the hive metastore. Whenever a partition
gets created, we run the registered command. 
> Several questions around option B are:
> 1. whether to support registration of HiveQL or shell command;
> 2. which machine/environment to run the command;
> 3. what to do if the registered command failed.

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