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https://issues.apache.org/jira/browse/HIVE-887?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12802105#action_12802105
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Ning Zhang commented on HIVE-887:
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Eric, we were discussing the same thing before to allow simple where-clause to
the non-MR client side execution. This woud be straightforward after we make
fetchOperator extends Operator. Then basically any map-only plan (including
map-side joins) could be move to non-MR execution.
The only thing I'm not sure about is the "fetch n" syntax. Since we don't have
stats, we don't know the number of rows in the input file. So as a first step
we can rely on the file size.
> 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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