Hello
I was wondering if it is normal on your installations to have users that
belong to several groups.
If positive, how much and what time does it take to show the first step on
the backend?
In our installations of DSpace there are about 10 people that belong to more
than 20 groups.
First step to show list of groups takes around 20-25 seconds. Thats a lot.
Is there any fix to this inefficient query?
Test it on
- Red Hat EL 5.5 (Tikanga)
- DSpace 1.5.1
- Postgresql 8.4.2
- Tomcat 6.0.33
- java version "1.6.0_30"
select eperson.eperson_id, count(*) as num from eperson,epersongroup2eperson
where eperson.eperson_id=epersongroup2eperson.eperson_id group by
eperson.eperson_id order by count(*) desc limit 10;
eperson_id | num
------------+-----
24 | 171
278 | 94
30 | 87
7 | 66
386 | 60
482 | 55
454 | 16
304 | 12
640 | 11
347 | 10
(10 filas)
dspace=# explain analyze SELECT * FROM group2groupcache WHERE child_id in
(select eperson_group_id from epersongroup2eperson where eperson_id=24);
QUERY
PLAN
----------------------------------------------------------------------------
------------------------------------------------------------------------
Hash Join (cost=16.23..112.81 rows=4158 width=12) (actual
time=5.575..18.461 rows=877 loops=1)
Hash Cond: (group2groupcache.child_id =
epersongroup2eperson.eperson_group_id)
-> Seq Scan on group2groupcache (cost=0.00..64.58 rows=4158 width=12)
(actual time=5.245..17.415 rows=4158 loops=1)
-> Hash (cost=15.07..15.07 rows=93 width=4) (actual time=0.296..0.296
rows=171 loops=1)
-> HashAggregate (cost=14.14..15.07 rows=93 width=4) (actual
time=0.233..0.260 rows=171 loops=1)
-> Bitmap Heap Scan on epersongroup2eperson
(cost=5.58..13.71 rows=171 width=4) (actual time=0.085..0.162 rows=171
loops=1)
Recheck Cond: (eperson_id = 24)
-> Bitmap Index Scan on epg2ep_eperson_fk_idx
(cost=0.00..5.53 rows=171 width=0) (actual time=0.060..0.060 rows=171
loops=1)
Index Cond: (eperson_id = 24)
Total runtime: 18.577 ms
(10 filas)
cid:f0154016-8e66-4c6b-9255-4e7524133341
Evelio Martínez
Director proyectos software.
CISA, CCNA
Dept. de Tecnologías y Sistemas de Información
C/ Garcilaso, 15-bajo
46003 Valencia
Telf: 96 369 41 23 / 677 405 909
Fax: 96 369 34 39
<http://www.masmedios.com/> www.masmedios.com
cid:f0154016-8e66-4c6b-9255-4e7524133341
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