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From "Ning Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-2165) variable to be assigned with an atomic value from a query
Date Fri, 13 May 2011 21:54:47 GMT

    [ https://issues.apache.org/jira/browse/HIVE-2165?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13033332#comment-13033332
] 

Ning Zhang commented on HIVE-2165:
----------------------------------

Yeah, I think we should draw a line between a necessary feature and a whole SP language. This
small feature can solve some cases that prevent hive from being a data flow processing language
itself, but I don't think a lot of features in SP language is necessary because they can be
implemented by Hive's UDFs (transform etc.). And UDFs have the benefits of pushing down computation
close to data. So I think implementing a full-blown SP's control flow is an overkill and unnecessary,
but some small feature like this has its value. 

> variable to be assigned with an atomic value from a query
> ---------------------------------------------------------
>
>                 Key: HIVE-2165
>                 URL: https://issues.apache.org/jira/browse/HIVE-2165
>             Project: Hive
>          Issue Type: Sub-task
>          Components: Query Processor
>            Reporter: Ning Zhang
>
> Currently variable can only be assigned by a constant. There are cases where a query
generate a single value that should be used by the second query. It would be nice to assign
this value to a variable and pass it to the second query. For exmaple:
> {code}
> hive> set x_avg = `select avg(x) from T`;
> hive> select my_udf(${hiveconf:x_avg}, y) from T2;
> {code}

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