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From "Samarth Jain (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PHOENIX-2943) Performance of parallel order by query is > 30X slower than serial execution
Date Sat, 28 May 2016 00:34:12 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-2943?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15305043#comment-15305043
] 

Samarth Jain commented on PHOENIX-2943:
---------------------------------------

[~mujtabachohan] - does it make a difference if stats aren't available? Makes me think it
would be nice to have a NO_STATS hint which would make testing things like these much easier.
It would also provide another performance comparison tool in our arsenal including SERIAL
and NO_CACHE.

> Performance of parallel order by query is > 30X slower than serial execution
> ----------------------------------------------------------------------------
>
>                 Key: PHOENIX-2943
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-2943
>             Project: Phoenix
>          Issue Type: Bug
>            Reporter: Mujtaba Chohan
>             Fix For: 4.8.0
>
>
> {code}
> select /*+SERIAL*/  L_DISCOUNT, L_QUANTITY from lineitem_encoded order by (l_discount,L_QUANTITY)
limit 1;
> +-------------+-------------+
> | L_DISCOUNT  | L_QUANTITY  |
> +-------------+-------------+
> | 0.04        | 17          |
> +-------------+-------------+
> 1 row selected (0.129 seconds)
> select L_DISCOUNT, L_QUANTITY from lineitem_encoded order by (l_discount,L_QUANTITY)
limit 1;
> +-------------+-------------+
> | L_DISCOUNT  | L_QUANTITY  |
> +-------------+-------------+
> | 0.04        | 17          |
> +-------------+-------------+
> 1 row selected (4.63 seconds)
> explain select /*+SERIAL*/  L_DISCOUNT, L_QUANTITY from lineitem_encoded order by (l_discount,L_QUANTITY)
limit 1;
> +------------------------------------------------------------------------------------------------+
> |                                              PLAN                                 
            |
> +------------------------------------------------------------------------------------------------+
> | CLIENT 417-CHUNK 5978838 ROWS 4150009682 BYTES SERIAL 417-WAY FULL SCAN OVER LINEITEM_ENCODED
 |
> |     SERVER TOP 1 ROW SORTED BY [(L_DISCOUNT, L_QUANTITY)]                         
            |
> | CLIENT MERGE SORT                                                                 
            |
> +------------------------------------------------------------------------------------------------+
> 3 rows selected (0.016 seconds)
> 0: jdbc:phoenix:localhost> explain select  L_DISCOUNT, L_QUANTITY from lineitem_encoded
order by (l_discount,L_QUANTITY) limit 1;
> +--------------------------------------------------------------------------------------------------+
> |                                               PLAN                                
              |
> +--------------------------------------------------------------------------------------------------+
> | CLIENT 417-CHUNK 5978838 ROWS 4150009682 BYTES PARALLEL 417-WAY FULL SCAN OVER LINEITEM_ENCODED
 |
> |     SERVER TOP 1 ROW SORTED BY [(L_DISCOUNT, L_QUANTITY)]                         
              |
> | CLIENT MERGE SORT                                                                 
              |
> +--------------------------------------------------------------------------------------------------+
> 3 rows selected (0.015 seconds)
> {code}
> Profiler information on this to be added soon. 



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