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From "Edward Capriolo (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-1096) Hive Variables
Date Fri, 19 Feb 2010 20:40:27 GMT

    [ https://issues.apache.org/jira/browse/HIVE-1096?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12835942#action_12835942
] 

Edward Capriolo commented on HIVE-1096:
---------------------------------------

{quote}
In your example, what do the "env" and "property" namespaces signify? Are these environment
variables and and system properties, respectively?
{quote}

Sorry I misread something you posted above. To be double clear :)

{noformat}
${hiveconf:variable_name}. --hive conf   && also SET
${env:variable_name}. --environmental properties
${system:property_name}-- java/system properties
${default:variable_name}. --set with -hivevar x=y
{noformat}

I understand you want to introduce  '-hivevar x' to create a very clear separation. Do you
think we need to go this far? As far as I know properties and environment are mostly unused
by hive. 

I am looking at this from terms of a new end user to hive. The simple part about my 1096-9.diff
is we were expanding upon the 'SET' and '-hiveconf'. What we have arrived at is cleaner but
more complex, and now we have to dip into the SetProcessor and introduce a new switch. 

I am ok with the more complex approach however. Does anyone else want to chime in?

> Hive Variables
> --------------
>
>                 Key: HIVE-1096
>                 URL: https://issues.apache.org/jira/browse/HIVE-1096
>             Project: Hadoop Hive
>          Issue Type: New Feature
>            Reporter: Edward Capriolo
>            Assignee: Edward Capriolo
>         Attachments: 1096-9.diff, hive-1096-2.diff, hive-1096-7.diff, hive-1096-8.diff,
hive-1096.diff
>
>
> From mailing list:
> --Amazon Elastic MapReduce version of Hive seems to have a nice feature called "Variables."
Basically you can define a variable via command-line while invoking hive with -d DT=2009-12-09
and then refer to the variable via ${DT} within the hive queries. This could be extremely
useful. I can't seem to find this feature even on trunk. Is this feature currently anywhere
in the roadmap?--
> This could be implemented in many places.
> A simple place to put this is 
> in Driver.compile or Driver.run we can do string substitutions at that level, and further
downstream need not be effected. 
> There could be some benefits to doing this further downstream, parser,plan. but based
on the simple needs we may not need to overthink this.
> I will get started on implementing in compile unless someone wants to discuss this more.

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