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From Priyanka Ganuthula <priya...@gmail.com>
Subject Re: Slow Reads
Date Tue, 26 Jul 2011 17:23:40 GMT
Thanks Philippe , I have a question here...I am specifying the required
super column.Does it still need to read the entire row?
Or is it because am listing all the slices and then going to each slice and
picking data for the required super column?
SlicePredicate slicePredicate = new SlicePredicate();
SliceRange sliceRange = new SliceRange();
sliceRange.setStart(new byte[] {});
sliceRange.setFinish(new byte[] {});
slicePredicate.setSlice_range(sliceRange);


ColumnParent columnParent = new ColumnParent(COLUMN_FAMILY);
KeyRange keyRange = new KeyRange();
keyRange.start_key= ByteBuffer.wrap(lastkey.getBytes());
keyRange.end_key=ByteBuffer.wrap("".getBytes());


List<KeySlice> slices = client.get_range_slices(columnParent,
slicePredicate, keyRange, ConsistencyLevel.ONE);

Then i loop around slices and  and list super columns and set the name of
the super column and look for that.

Am I missing sth here ?

On Tue, Jul 26, 2011 at 11:59 AM, Philippe <watcherfr@gmail.com> wrote:

> i believe it's because it needs to read the whole row to get to your super
> column.
>
> you might have to reconsider your model.
> Le 26 juil. 2011 17:39, "Priyanka" <priya429@gmail.com> a écrit :
>
> >
> > Hello All,
> >
> > I am doing some read tests on Cassandra on a single node.But they
> > are turning up to be very slow.
> > Here is the data model in detail.
> > I am using a super column family.Cassandra has total 970 rows and each
> row
> > has 620901 super columns and each super column has 2 columns.Total data
> in
> > the database would be around 45GB.
> > I am trying to retrieve the data of a particular super column[Trying to
> pull
> > the row key associated with the super column and the column values with
> in
> > the super column.
> > It is taking 2.5 secs with java code and 4.7 secs with the python code.
> >
> > Here is the python code.
> > result = col_fam.get_range(start="",
> > finish="",columns=None,column_start="",column_finish
> >
> ="",column_reversed=False,column_count=2,row_count=None,include_timestamp=False,
> > super_column='200003', read_consistency_level=None,buffer_size=None)
> >
> > This is very slow compared to MySQL.
> > Am not sure whats going wrong here.Could some one let me know if there is
> > any problem with my model.
> >
> >
> > Any help in this regard is highly appreciated.
> >
> > Thank you.
> >
> > Regards,
> > Priyanka
> >
> >
> >
> >
> >
> > --
> > View this message in context:
> http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/Slow-Reads-tp6622680p6622680.html
> > Sent from the cassandra-user@incubator.apache.org mailing list archive
> at Nabble.com.
>

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