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From Dan Washusen <...@reactive.org>
Subject Re: Are row-keys sorted by the compareWith?
Date Mon, 21 Feb 2011 03:23:49 GMT
Hi Carlo,
As Jonathan mentions the compareWith on a column family def. is defines the order for the
columns *within* a row... In order to control the ordering of rows you'll need to use the
OrderPreservingPartitioner (http://www.datastax.com/docs/0.7/operations/clustering#tokens-partitioners-ring).


As for getColumnsFromRows; it should be returning you a map of lists. The map is insertion-order-preserving
and populated based on the provided list of row keys (so if you iterate over the entries in
the map they should be in the same order as the list of row keys). The list for each row entry
are definitely in the order that Cassandra provides them, take a look at org.scale7.cassandra.pelops.Selector#toColumnList
if you need more info.

Cheers,
Dan

-- 
Dan Washusen
Sent with Sparrow
On Saturday, 19 February 2011 at 8:16 AM, cbertu81@libero.it wrote: 
> Hi all,
> I created a CF in which i need to get, sorted by time, the Rows inside. Each 
> Row represents a comment.
> 
> <ColumnFamily name="Comments" compareWith="TimeUUIDType" / >
> 
> I've created a few rows using as Row Key a generated TimeUUID but when I call 
> the Pelops method "GetColumnsFromRows" I don't get the data back as I expect: 
> rows are not sorted by TimeUUID.
> I though it was probably cause of the random-part of the TimeUUID so I create 
> a new CF ...
> 
> <ColumnFamily name="Comments2" compareWith="LongType" / >
> 
> This time I created a few rows using the java System.CurrentTimeMillis() that 
> retrieve a long. I call again the "GetColumnsFromRows" and again the same 
> results: data are not sorted!
> I've read many times that Rows are sorted as specified in the compareWith but 
> I can't see it. 
> To solve this problem for the moment I've used a SuperColumnFamily with an 
> UNIQUE ROW ... but I think this is just a workaround and not the solution.
> 
> <ColumnFamily name="Comments" type="Super" compareWith="TimeUUIDType" 
> CompareSubcolumnsWith="BytesType"/ >
> 
> Now when I call the "GetSuperColumnsFromRow" I get all the SuperColumns as I 
> expected: sorted by TimeUUID. Why it does not happen the same with the Rows? 
> I'm confused.
> 
> TIA for any help.
> 
> Best Regards
> 
> Carlo
> 

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