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https://issues.apache.org/jira/browse/HIVE-1096?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12835785#action_12835785
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Edward Capriolo commented on HIVE-1096:
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{quote}
True, but I think we should try to improve the situation. As a start we can add
code to throw an error if hive-default.xml or hive-site.xml sets a hive.*
configuration property that is not defined in HiveConf. This would protect the
hive.* namespace and at the same time make it easy to track down cases where
folks misspell a hive.* property name.
{quote}
I only see one problem with this. HiveConf has an enumeration of valid
properties. I do not think Hadoop Conf shares that trait. So if someone were to
say:
{noformat}
set hadoop.wrong.variable.name
{noformat}
Would we have a simple way of knowing if that variable was variable is valid.
Anyway that is out of scope a bit.
{quote}
${namespace:variable_name}.
{quote}
I like this. How about?
{noformat}
${hiveconf:variable_name}.
${env:variable_name}.
${property:variable_name}.
{noformat}
This way we do not need the "-hivevar x=y" switch." I say this because we
already have three mechanism to pass data into Java/hive adding a forth is a
little confusing.
The only problem with introducing this is now we have a new question. How do we
extend SET to read/write these?
> 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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