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From Ashish Thusoo <athu...@qubole.com>
Subject Re: how to select without Mapreduce after index build?
Date Fri, 11 May 2012 16:17:44 GMT
Indexing in Hive works through map/reduce. There are no active components
in Hive (such as the region servers in Hbase), so the way the index is
basically used is by running the map/reduce job on the table that holds the
index data to get all the relevant offsets into the main table and then
using those offsets to figure out which blocks to read from the main table.
So you will not see map/reduce go away even when you are running queries on
tables with indexes on them.

Ashish

On Thu, May 10, 2012 at 11:32 PM, Hezhiqiang (Ransom) <
ransom.hezhiqiang@huawei.com> wrote:

>  I think if I  create index for one table****
>
> When I excute “select c1,c2 from tab where index_col=1”, should not start
> mapreduce****
>
> But it was start .****
>
> So how to use a index without mapreduce?****
>
> Compact  index and bitmap index all was tested , all need mapreduce . ****
>

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