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From Frank LoVecchio <fr...@isidorey.com>
Subject Re: Range Queries in RP on SCF in 0.7 with UUID SCs
Date Wed, 01 Dec 2010 22:03:34 GMT
Hey Aaron,


Yes, in regards to SCF definition, you are correct:


name: Sensor

      column_type: Super

      compare_with: TimeUUIDType

      gc_grace_seconds: 864000

      keys_cached: 10000.0

      read_repair_chance: 1.0

      rows_cached: 0.0

I'm not quite sure I follow you, though, as I think I'm doing what you
specify.  The Pelops code is below.  Basically, I want to get rows starting
from a Super Column with a specific UUID and limit the number, just as you
inferred.  When I run this code I just get the last N values (25 in this
case) if non-reversed, and the first N values if reversed.  However,
regardless of what start param we use (Super Column UUID is String startKey
below), we still get the same values for the specified amount (e.g. the same
25).

*public* *void* getSuperRowKeys(String rowKey, String columnFamily,
*int* limit,
String startKey) *throws* Exception {

 *byte*[] byteArray = UuidHelper.*timeUuidStringToBytes*(startKey);

ByteBuffer bb = ByteBuffer.*wrap*(byteArray);

*new* UUID (bb.getLong(), bb.getLong());

 List<SuperColumn> cols = selector.getPageOfSuperColumnsFromRow(columnFamily,
rowKey, Bytes.*fromByteBuffer*(bb), *false*, limit, ConsistencyLevel.*ONE*);


 *for* (SuperColumn col : cols) {

*if* (col.getName() != *null*) {


System.*out*.println("NAME: " + UUID.*nameUUIDFromBytes*(col.getName()));


*for* (Column c : col.columns) {

System.*out*.println("\t\tName: " + Bytes.*toUTF8*(c.getName())

+ " Value: " + Bytes.*toUTF8*(c.getValue())

+ " timestamp: " + c.timestamp);


}


}

}


}

Here is some example data from the CLI.  If we specify
2f814d30-f758-11df-2f81-4d30f75811df
as the start param (second super column down), we still get
52e6540-f759-11df-952e-6540f75911df
(first super column) returned.

=> (super_column=952e6540-f759-11df-952e-6540f75911df,
     (column=64617465, value=323031302d31312d32332032333a32393a30332e303030,
timestamp=1290554997141000)
     (column=65787472615f696e666f, value=6e6f6e65,
timestamp=1290554997141000)
     (column=726561736f6e, value=6e6f6e65, timestamp=1290554997141000)
     (column=7365636f6e64735f746f5f6e657874, value=373530,
timestamp=1290554997141000)
     (column=73657269616c, value=393135353032353731,
timestamp=1290554997141000)
     (column=737461747573, value=5550, timestamp=1290554997141000)
     (column=74797065, value=486561727462656174,
timestamp=1290554997141000))
=> (super_column=2f814d30-f758-11df-2f81-4d30f75811df,
     (column=64617465, value=323031302d31312d32332032333a31393a30332e303030,
timestamp=1290554397060000)
     (column=65787472615f696e666f, value=6e6f6e65,
timestamp=1290554397060000)
     (column=726561736f6e, value=6e6f6e65, timestamp=1290554397060000)
     (column=7365636f6e64735f746f5f6e657874, value=373530,
timestamp=1290554397060000)
     (column=73657269616c, value=393135353032353731,
timestamp=1290554397060000)
     (column=737461747573, value=5550, timestamp=1290554397060000)
     (column=74797065, value=486561727462656174,
timestamp=1290554397060000))
=> (super_column=7c959f00-f757-11df-7c95-9f00f75711df,
     (column=64617465, value=323031302d31312d32332032333a31343a30332e303030,
timestamp=1290554096881000)
     (column=65787472615f696e666f, value=6e6f6e65,
timestamp=1290554096881000)
     (column=726561736f6e, value=6e6f6e65, timestamp=1290554096881000)
     (column=7365636f6e64735f746f5f6e657874, value=373530,
timestamp=1290554096881000)
     (column=73657269616c, value=393135353032353731,
timestamp=1290554096881000)
     (column=737461747573, value=5550, timestamp=1290554096881000)
     (column=74797065, value=486561727462656174,
timestamp=1290554096881000))
=> (super_column=c9be6330-f756-11df-c9be-6330f75611df,
     (column=64617465, value=323031302d31312d32332032333a30393a30332e303030,
timestamp=1290553796836000)
     (column=65787472615f696e666f, value=6e6f6e65,
timestamp=1290553796836000)
     (column=726561736f6e, value=6e6f6e65, timestamp=1290553796836000)
     (column=7365636f6e64735f746f5f6e657874, value=373530,
timestamp=1290553796836000)
     (column=73657269616c, value=393135353032353731,
timestamp=1290553796836000)
     (column=737461747573, value=5550, timestamp=1290553796836000)
     (column=74797065, value=486561727462656174,
timestamp=1290553796836000))
=> (super_column=17108150-f756-11df-1710-8150f75611df,
     (column=64617465, value=323031302d31312d32332032333a30343a30332e303030,
timestamp=1290553497067000)
     (column=65787472615f696e666f, value=6e6f6e65,
timestamp=1290553497067000)
     (column=726561736f6e, value=6e6f6e65, timestamp=1290553497067000)
     (column=7365636f6e64735f746f5f6e657874, value=373530,
timestamp=1290553497067000)
     (column=73657269616c, value=393135353032353731,
timestamp=1290553497067000)
     (column=737461747573, value=5550, timestamp=1290553497067000)
     (column=74797065, value=486561727462656174,
timestamp=1290553497067000))
=> (super_column=641da730-f755-11df-641d-a730f75511df,
     (column=64617465, value=323031302d31312d32332032323a35393a30332e303030,
timestamp=1290553196836000)
     (column=65787472615f696e666f, value=6e6f6e65,
timestamp=1290553196836000)
     (column=726561736f6e, value=6e6f6e65, timestamp=1290553196836000)
     (column=7365636f6e64735f746f5f6e657874, value=373530,
timestamp=1290553196836000)
     (column=73657269616c, value=393135353032353731,
timestamp=1290553196836000)
     (column=737461747573, value=5550, timestamp=1290553196836000)
     (column=74797065, value=486561727462656174,
timestamp=1290553196836000))
=> (super_column=4bce9420-f753-11df-4bce-9420f75311df,
     (column=64617465, value=323031302d31312d32332032323a34343a30332e303030,
timestamp=1290552297060000)
     (column=65787472615f696e666f, value=6e6f6e65,
timestamp=1290552297060000)
     (column=726561736f6e, value=6e6f6e65, timestamp=1290552297060000)
     (column=7365636f6e64735f746f5f6e657874, value=373530,
timestamp=1290552297060000)
     (column=73657269616c, value=393135353032353731,
timestamp=1290552297060000)
     (column=737461747573, value=5550, timestamp=1290552297060000)
     (column=74797065, value=486561727462656174,
timestamp=1290552297060000))

On Wed, Dec 1, 2010 at 2:25 PM, Aaron Morton <aaron@thelastpickle.com>wrote:

> The Partitioner applies to the row keys, not the columns. Their order is
> determined by the compare_with and compare_subcolumns_with CF settings
>
> So where you say "get the last 25 inserts for a key" I'm translating that
> into "get the most recent 25 super columns for a row, where the super column
> names are UUID's and the CF definition has compare_with:  TimeUUIDType"
>
> You can send a get_slice where the SliceRange has count=25 and
> reversed=True. If you know the 25th col name you can use it as the start
> param, and AFAIK the operation would go faster. Not sure how this translates
> into calls against Pelops.
>
> This assumes you are using time / v1 UUID's that have an increasing order.
>
> Hope that helps.
>
> Aaron
>
>
> On 02 Dec, 2010,at 09:19 AM, Frank LoVecchio <frank@isidorey.com> wrote:
>
> Is it possible to perform paginated queries using Random Partitioner in 0.7
> with Super Column Families whose Super Columns are UUID's?  I don't believe
> it is, based on this article:
> http://ria101.wordpress.com/2010/02/22/cassandra-randompartitioner-vs-orderpreservingpartitioner,
> and my attempts with Pelops.
>
> Let's say I get the last 25 inserts for a key.  I now know the 25th Super
> Column UUID, and I want to start from there and get the next 25 inserts.  Do
> I have to change over to Order Preserving Partitioner?  I'd like to avoid
> this at all costs.
>
> Thanks,
>
> Frank
>
>

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