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https://issues.apache.org/jira/browse/HAWQ-1183?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Paul Guo reassigned HAWQ-1183:
------------------------------

    Assignee: Paul Guo  (was: Lei Chang)

> Writable external table with Hash distribution shows slow performance
> ---------------------------------------------------------------------
>
>                 Key: HAWQ-1183
>                 URL: https://issues.apache.org/jira/browse/HAWQ-1183
>             Project: Apache HAWQ
>          Issue Type: Bug
>            Reporter: Paul Guo
>            Assignee: Paul Guo
>
> Steps:
> 1. Create tables and populate them.
> drop table tbl1;
> drop external table ext_tbl1;
> drop external table ext_tbl1_random;
> CREATE TABLE tbl1 (a int, b text) DISTRIBUTED BY (a);
> INSERT INTO tbl1 VALUES (generate_series(1,1000),'aaa');
> INSERT INTO tbl1 VALUES (generate_series(1,10000),'bbb');
> INSERT INTO tbl1 VALUES (generate_series(1,100000),'bbc');
> INSERT INTO tbl1 VALUES (generate_series(1,1000000),'bdbc');
> INSERT INTO tbl1 VALUES (generate_series(1,1000000),'bdddbc');
> CREATE WRITABLE EXTERNAL TABLE ext_tbl1
> ( LIKE tbl1 )
> LOCATION ('gpfdist://127.0.0.1/tbl1.csv')
> FORMAT 'CSV' (DELIMITER ',')
> DISTRIBUTED BY (a);
> CREATE WRITABLE EXTERNAL TABLE ext_tbl1_random
> ( LIKE tbl1 )
> LOCATION ('gpfdist://127.0.0.1/tbl1.random.csv')
> FORMAT 'CSV' (DELIMITER ',')
> DISTRIBUTED RANDOMLY;
> 2. Write the two external tables. We can find that the external table with 
> hash distribution is slow with inserting, and plan shows that it has 1 
> workers only.
> postgres=# explain analyze INSERT INTO ext_tbl1 SELECT * from tbl1;
>                             QUERY PLAN
> -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> -------------------------------------------------------------------
>  Insert  (cost=0.00..509.20 rows=1000 width=8)
>    Rows out:  Avg 2111000.0 rows x 1 workers.  
> Max/Last(seg0:host67/seg0:host67) 2111000/2111000 rows with 70/70 ms to first 
> row, 20304/20304 ms to end, start offset by 30/30 ms.
>    Executor memory:  1K bytes.
>    ->  Result  (cost=0.00..431.07 rows=1000 width=20)
>          Rows out:  Avg 2111000.0 rows x 1 workers.  
> Max/Last(seg0:host67/seg0:host67) 2111000/2111000 rows with 61/61 ms to first 
> row, 2034/2034 ms to end, start offset by 30/30 ms
> .
>          ->  Redistribute Motion 1:1  (slice1; segments: 1)  
> (cost=0.00..431.05 rows=1000 width=8)
>                Hash Key: tbl1.a
>                Rows out:  Avg 2111000.0 rows x 1 workers at destination.  
> Max/Last(seg0:host67/seg0:host67) 2111000/2111000 rows with 61/61 ms to first 
> row, 1370/1370 ms to end, sta
> rt offset by 30/30 ms.
>                ->  Table Scan on tbl1  (cost=0.00..431.01 rows=1000 width=8)
>                      Rows out:  Avg 2111000.0 rows x 1 workers.  
> Max/Last(seg0:host67/seg0:host67) 2111000/2111000 rows with 61/61 ms to first 
> row, 566/566 ms to end, start offset b
> y 30/30 ms.
>  Slice statistics:
>    (slice0)    Executor memory: 293K bytes (seg0:host67).
>    (slice1)    Executor memory: 303K bytes (seg0:host67).
>  Statement statistics:
>    Memory used: 262144K bytes
>  Optimizer status: PQO version 1.684
>  Dispatcher statistics:
>    executors used(total/cached/new connection): (2/0/2); dispatcher 
> time(total/connection/dispatch data): (17.095 ms/16.477 ms/0.053 ms).
>    dispatch data time(max/min/avg): (0.027 ms/0.025 ms/0.026 ms); consume 
> executor data time(max/min/avg): (0.051 ms/0.043 ms/0.047 ms); free executor 
> time(max/min/avg): (0.000 ms/0
> .000 ms/0.000 ms).
>  Data locality statistics:
>    data locality ratio: 1.000; virtual segment number: 1; different host 
> number: 1; virtual segment number per host(avg/min/max): (1/1/1); segment 
> size(avg/min/max): (46023656.000 B
> /46023656 B/46023656 B); segment size with penalty(avg/min/max): 
> (46023656.000 B/46023656 B/46023656 B); continuity(avg/min/max): 
> (1.000/1.000/1.000); DFS metadatacache: 46.181 ms;
> resource allocation: 1.837 ms; datalocality calculation: 1.180 ms.
>  Total runtime: 20538.524 ms
> (22 rows)
> postgres=# explain analyze INSERT INTO ext_tbl1 SELECT * from tbl1;
>                  QUERY PLAN
> -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> --------------------------------------------
>  Insert  (cost=0.00..444.03 rows=167 width=8)
>    Rows out:  Avg 351833.3 rows x 6 workers.  
> Max/Last(seg5:host67/seg0:host67) 351916/351849 rows with 89/171 ms to first 
> row, 4074/4209 ms to end, start offset by 46/45 ms.
>    Executor memory:  1K bytes avg, 1K bytes max (seg5:host67).
>    ->  Result  (cost=0.00..431.01 rows=167 width=20)
>          Rows out:  Avg 351833.3 rows x 6 workers.  
> Max/Last(seg5:host67/seg0:host67) 351916/351849 rows with 77/148 ms to first 
> row, 292/392 ms to end, start offset by 46/45 ms.
>          ->  Table Scan on tbl1  (cost=0.00..431.00 rows=167 width=8)
>                Rows out:  Avg 351833.3 rows x 6 workers.  
> Max/Last(seg5:host67/seg2:host67) 351916/351855 rows with 77/152 ms to first 
> row, 158/257 ms to end, start offset by 46/42
> ms.
>  Slice statistics:
>    (slice0)    Executor memory: 280K bytes avg x 6 workers, 280K bytes max 
> (seg5:host67).
>  Statement statistics:
>    Memory used: 262144K bytes
>  Optimizer status: PQO version 1.684
>  Dispatcher statistics:
>    executors used(total/cached/new connection): (6/0/6); dispatcher 
> time(total/connection/dispatch data): (38.288 ms/37.708 ms/0.078 ms).
>    dispatch data time(max/min/avg): (0.028 ms/0.004 ms/0.012 ms); consume 
> executor data time(max/min/avg): (0.067 ms/0.014 ms/0.029 ms); free executor 
> time(max/min/avg): (0.000 ms/0
> .000 ms/0.000 ms).
>  Data locality statistics:
>    data locality ratio: 1.000; virtual segment number: 6; different host 
> number: 1; virtual segment number per host(avg/min/max): (6/6/6); segment 
> size(avg/min/max): (7670609.333 B/
> 7668464 B/7672344 B); segment size with penalty(avg/min/max): (0.000 B/0 B/0 
> B); continuity(avg/min/max): (1.000/1.000/1.000); DFS metadatacache: 28.855 
> ms; resource allocation: 12.
> 933 ms; datalocality calculation: 0.190 ms.
>  Total runtime: 4333.663 ms
> (18 rows)



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