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From Sachin Katakdound <sachin.katakdo...@gmail.com>
Subject Re: Order by/limit clause on partitioned data
Date Sat, 19 Dec 2015 01:22:16 GMT

Thanks for quick reply.

We are using 4.2+ version at the moment, will that be a problem? Or is this a default behavior
in all the version of Phoenix? 

Regards,
Sachin

> On Dec 13, 2015, at 4:17 PM, James Taylor <jamestaylor@apache.org> wrote:
> 
> bq. When this simple query with Order by and limit clause is executed, does it return
a valid data considering the fact that the data will be spread across 4 region servers?
> Yes
> 
> bq. Does this mean that 15 rows are gathered from each region server and then the limit
clause applied on the client?
> Yes
> 
> bq. How exactly is this query executed?
> It's executed as you've described. Each parallel scan that Phoenix runs returns the top
15 rows (as determined by the ORDER BY clause). The results of these scans are merge sorted
on the client with the top 15 rows being returned.
> 
> On Sat, Dec 12, 2015 at 10:24 PM, Sachin Katakdound <sachin.katakdound@gmail.com <mailto:sachin.katakdound@gmail.com>>
wrote:
> Let’s say we have a simple (phoenix table) data set.
> 
> create table ADDRESS(“id” NUMBER primary key,
>         “city” VARCHAR,
>         "state” VARCHAR,
>         “zip”   VARCHAR) SALT_BUCKETS=4
> 
> And lets suppose there are 4 different region servers, and this data set is spread across
4 separate regions.
> 
> Now, the following query is run;
> select * from ADDRESS order by “city” limit 15;
> 
> When this simple query with Order by and limit clause is executed, does it return a valid
data considering the fact that the data will be spread across 4 region servers?
> 
> I believe the query plan indicates “ordering on the server” and then limit clause
on the client.
> 
> Does this mean that 15 rows are gathered from each region server and then the limit clause
applied on the client?
> How exactly is this query executed?
> 
> Thanks in advance.
> 
> Regards,
> Sachin
> 
> 
> 
> 
> 


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