Re: Reverse sort on Primary Key

[Scott Reynolds]

Thanks guys thought it should be easy. I am looking to paginate through the
records, not return the most recent value.

If I need to toggle -- which I might -- I was planning on using token api.
The KuduScanToken actually implements Comparable and it's implementation is
around the tablet. I think this means you can sort the list of
KuduScanTokens and call out to each one sequentially. Does that sound crazy?

On Mon, Apr 23, 2018 at 3:23 PM Dan Burkert  wrote:

> Hey Scott,
>
> Patrick's answer is spot on.  I'm curious, though, is your usecase to find
> the latest value?  Effectively a 'SORT BY DESC date LIMIT 1', or are you
> looking for the last n values, or all values?  I ask because we frequently
> get the 'last value' question, and the solution for that might be more
> specific (and simpler) than a generalized reverse sort + limit.
>
> - Dan
>
> On Mon, Apr 23, 2018 at 1:25 PM, Patrick Angeles 
> wrote:
>
>> The common technique is to use (MAX_LONG - timestamp). Unfortunately this
>> won't let you toggle the sort order back-and-forth on the same table. You
>> could have a duplicate table with the inverse key, effectively using it as
>> a secondary index.
>>
>> As of version 0.98, HBase supports a reverse scan without a 'secondary
>> index' table (HBASE-4811), so with a bit of work Kudu may be able to
>> provide something similar.
>>
>>
>> Patrick Angeles
>> Chief Architect Financial Services
>> 151 West 26th Street Suite 1002 |
>> New
>> York, NY 10001
>> 
>> +1 (917) 633-4524 <(917)%20633-4524>
>>
>> On Sat, Apr 21, 2018 at 10:36 PM, Scott Reynolds 
>> wrote:
>>
>>> Today we are using Kudu  to store timeseries information and would like
>>> the ability to toggle the sort direction. It is unclear to me at the moment
>>> how to achieve this efficiently. I naively assumed Kudu could read the
>>> primary key in reverse but there doesn't appear to be the case ATM.
>>>
>>> If you were tasked with implementing a reverse sort on the primary key
>>> (Date Desc) how would you go about implementing it ?
>>>
>>> Thanks!
>>>
>>
>>
>

Re: Reverse sort on Primary Key

[Dan Burkert]

Hey Scott,

Patrick's answer is spot on.  I'm curious, though, is your usecase to find
the latest value?  Effectively a 'SORT BY DESC date LIMIT 1', or are you
looking for the last n values, or all values?  I ask because we frequently
get the 'last value' question, and the solution for that might be more
specific (and simpler) than a generalized reverse sort + limit.

- Dan

On Mon, Apr 23, 2018 at 1:25 PM, Patrick Angeles 
wrote:

> The common technique is to use (MAX_LONG - timestamp). Unfortunately this
> won't let you toggle the sort order back-and-forth on the same table. You
> could have a duplicate table with the inverse key, effectively using it as
> a secondary index.
>
> As of version 0.98, HBase supports a reverse scan without a 'secondary
> index' table (HBASE-4811), so with a bit of work Kudu may be able to
> provide something similar.
>
>
> Patrick Angeles
> Chief Architect Financial Services
> 151 West 26th Street Suite 1002 |
> New
> York, NY 10001
> 
> +1 (917) 633-4524
>
> On Sat, Apr 21, 2018 at 10:36 PM, Scott Reynolds 
> wrote:
>
>> Today we are using Kudu  to store timeseries information and would like
>> the ability to toggle the sort direction. It is unclear to me at the moment
>> how to achieve this efficiently. I naively assumed Kudu could read the
>> primary key in reverse but there doesn't appear to be the case ATM.
>>
>> If you were tasked with implementing a reverse sort on the primary key
>> (Date Desc) how would you go about implementing it ?
>>
>> Thanks!
>>
>
>

Re: Reverse sort on Primary Key

[Patrick Angeles]

The common technique is to use (MAX_LONG - timestamp). Unfortunately this
won't let you toggle the sort order back-and-forth on the same table. You
could have a duplicate table with the inverse key, effectively using it as
a secondary index.

As of version 0.98, HBase supports a reverse scan without a 'secondary
index' table (HBASE-4811), so with a bit of work Kudu may be able to
provide something similar.


Patrick Angeles
Chief Architect Financial Services
151 West 26th Street Suite 1002 | New York, NY 10001
+1 (917) 633-4524

On Sat, Apr 21, 2018 at 10:36 PM, Scott Reynolds 
wrote:

> Today we are using Kudu  to store timeseries information and would like
> the ability to toggle the sort direction. It is unclear to me at the moment
> how to achieve this efficiently. I naively assumed Kudu could read the
> primary key in reverse but there doesn't appear to be the case ATM.
>
> If you were tasked with implementing a reverse sort on the primary key
> (Date Desc) how would you go about implementing it ?
>
> Thanks!
>