Thanks Andrey. On 14 June 2017 at 20:15, Andrey Mashenkov <andrey.mashen...@gmail.com> wrote:
> Hi Anil, > > Yes, in your case map queries results already sorted and there is only > merge on reduce side. > Sorting can be disabled on map side when e.g. aggregates is used. > > On Wed, Jun 14, 2017 at 3:20 PM, Anil <anilk...@gmail.com> wrote: > >> Hi Team, >> >> Can some help in understanding the below ? Thanks. >> >> On 13 June 2017 at 11:07, Anil <anilk...@gmail.com> wrote: >> >>> HI Team, >>> >>> I have a table TEST with a indexed column COL_A. Does the following >>> query works ? >>> >>> select * from Test where COL_A > '1' and COL_A < '2' offset 10 ROWS >>> FETCH NEXT 20 ROWS ONLY >>> >>> As per my understanding of distributed systems, the query is sent to all >>> nodes and gets the 10 records from each node and return 10 (whatever >>> returns first) >>> >>> as indexes are distributed, the above query may not return the records >>> in paginated way without adding sort like below. >>> >>> select * from Test where COL_A > '1' and COL_A < '2' order by COL_A >>> offset 10 ROWS FETCH NEXT 20 ROWS ONLY >>> >>> do you see any overhead of sort here ? >>> >>> Does it work in following way ? >>> >>> send the query to all nodes and get 10 (based on sorting) records and >>> sort all results of each node at reducer and return final 10 . >>> >>> Sort should not have any overhead here as sort and filter is done on >>> indexed column. >>> >>> Please correct me if i am wrong. thanks. >>> >>> Thanks >>> >>> >> > > > -- > Best regards, > Andrey V. Mashenkov >
