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From Leo Alekseyev <dnqu...@gmail.com>
Subject Re: Possible to scan row keys only?
Date Thu, 23 Dec 2010 00:04:40 GMT
Looking at HBASE-1537, it seems that it only limits the number of
columns (or column families?) that the scanner returns.  This is not
useful to us; we have only one column with one column family.  One
solution might potentially be to add a dummy column family and then
use HBASE-1537 with a limit of 1.  We'd do it if it's the only option,
but we'd rather not online and offline our tables (we are talking
about many terabytes in a production cluster).

Is it somehow possible to use KeyValue.getRow() or KeyValue.getKey()
in a scanner without returning KeyValue's?  Basically, any code that
tries to return or make copies of entire KeyValue's is incredibly
inefficient, since (a) we only need the key and (b) sizeof(key) is
many orders of magnitude smaller than sizeof(value).

On Wed, Dec 22, 2010 at 1:53 PM, Ted Yu <yuzhihong@gmail.com> wrote:
> How about HBASE-1537 ?
> On Wed, Dec 22, 2010 at 1:38 PM, Leo Alekseyev <dnquark@gmail.com> wrote:
>> I need to retrieve row keys from several big tables.  Is it possible
>> to do so by just reading the key and truncating the value?  I see that
>> HBASE-1481 implements FirstKeyOnlyFilter, but it doesn't help in our
>> case, since we have only one KeyValue per row, and it stores binary
>> data.
>> Is there an easy way to accomplish fast key-only retrieval?
>> --Leo

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