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From "Ning Zhang (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-887) Allow SELECT <col> without a mapreduce job
Date Mon, 19 Oct 2009 18:29:59 GMT

    [ https://issues.apache.org/jira/browse/HIVE-887?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12767442#action_12767442
] 

Ning Zhang commented on HIVE-887:
---------------------------------

After looking more carefully at the code, the fetch task spawn a fetch operator at its initialization,
and the fetch operator is not subclass of Operator. So we probably need to extend it to Operator
class and make the select Operator as a child of fetch, or push select operator's logic to
fetch operator's implementation. Will have a discussion first and put it as a lower priority
in my task list for now. 

> Allow SELECT <col> without a mapreduce job
> ------------------------------------------
>
>                 Key: HIVE-887
>                 URL: https://issues.apache.org/jira/browse/HIVE-887
>             Project: Hadoop Hive
>          Issue Type: New Feature
>         Environment: All
>            Reporter: Eric Sun
>            Assignee: Ning Zhang
>
> I often find myself needing to take a quick look at a particular column of a Hive table.
> I usually do this by doing a 
> SELECT * from <table> LIMIT 20;
> from the CLI.  Doing this is pretty fast since it doesn't require a mapreduce job.  However,
it's tough to examine just 1 or 2 columns when the table is very wide.
> So, I might do
> SELECT <col> from <table> LIMIT 20;
> but it's much slower since it requires a map-reduce.  It'd be really convenient if a
map-reduce wasn't necessary.
> Currently a good work around is to do
> hive -e "select * from table" | cut --key=n
> but it'd be more convenient if it were built in since it alleviates the need for column
counting.

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