Re: Memory and performance

edipoelder(at)ig(dot)com(dot)br wrote:
>
> 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).

That's 50,000 inserts in one transaction - have you tried 50
transactions of 1000 inserts?

> I get as result, the following times:

> 5 | group 5 | 00:02:08
>
> 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?

I don't fancy your chances before 7.1 ;-)

> 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.

If you need to import large quantities of data, look at the copy
command, that tends to be faster.

- Richard Huxton