Memory and performance

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От edipoelder@ig.com.br
Тема Memory and performance
Дата
Msg-id 200104041715.f34HF8858323@postgresql.org
обсуждение исходный текст
Ответы Re: Memory and performance  (Tom Lane <tgl@sss.pgh.pa.us>)
Список pgsql-sql
Hi all, 
   I have noted that Postgresql don't make a good memory handle. I have 
made the tables/procedure (in attached file) and run it as "select bench(10, 
5000)". This will give a 50000 records inserts (5 x 10000). (well, I run it 
on a P200+64MB of RAM, under Linux, and Postgres 7.0.2. In a more powerfull 
machine, you can try other values). 
   I get as result, the following times: 
id | objname | benchtime 
----+---------+-----------  1 | group 1 | 00:00:32  2 | group 2 | 00:00:47  3 | group 3 | 00:01:13  4 | group 4 |
00:01:41 5 | group 5 | 00:02:08 
 
(5 rows) 
   Note that, with memory increse, the system becomes slow, even if the 
system has free memory to alocate (yes, 64MB is enough to this test). I 
didn't see the source code (yet), but I think that the data estructure used 
to keep the changed records is a kind of chained list; and to insert a new 
item, you have to walk to the end of this list. Can it be otimized? 
   The system that I'm developing, I have about 25000 (persons) x 8 (exams) 
x 15 (answers per exam) = 3000000 records to process and it is VERY SLOW. 
   thanks, 
   Edipo Elder    [edipoelder@ig.com.br] 

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