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Re: [Springframework-developer] JdbcHelper
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From: <tri...@tr...> - 2004-02-27 22:31:55
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Quoting Eduardo Issao Ito <zi...@su...>:
>
> So ArrayList seems ok for this usage, and we have quick random access also!
>
> As usual in the performance area, our intuition is not so useful as a simple
>
> benchmark...
>
> Thanks!
>
>
> PS: Why that (almost) empty loop? The question was about how to populate the
> List.
I thought it would be more realistic test if we actually did something with the
list rather tan just populate it and throw it away.
Thomas
>
>
> tri...@tr... wrote:
>
> > Here is a quick unscientific benchmark:
> >
> > JdbcTemplate jt = new JdbcTemplate(ds);
> > String sql = "select * from my_large_table where rownum <= 200000";
> > long start = System.currentTimeMillis();
> > List l = jt.queryForList(sql);
> > int x = 0;
> > for (int i = 0; i < l.size(); i++) {
> > x++;
> > }
> > long done = System.currentTimeMillis();
> > System.out.println(": " + x + " in " + (done - start) + "ms");
> >
> > And the results:
> >
> > java.util.LinkedList: 2000 in 1156ms
> > java.util.ArrayList: 2000 in 1156ms
> >
> > java.util.LinkedList: 20000 in 5968ms
> > java.util.ArrayList: 20000 in 6031ms
> >
> > java.util.LinkedList: 200000 in 52154ms
> > java.util.ArrayList: 200000 in 52639ms
> >
> > As you can see the difference is very small. Most of the time is spent
> reading
> > the data from the database so the List processing only make up a tiny
> fraction
> > of the total time. I looked at the memory usage during the 200000 row runs
> and
> > these were the numbers:
> >
> > java.util.LinkedList: [196MB]
> > java.util.ArrayList: [192MB]
> >
> > Thomas
> >
> >
> >
> > Quoting tri...@tr...:
> >
> >
> >>Eduardo,
> >>
> >>I assume that you mean the new JdbcTemplate.queryForList()
> >>
> >>It's an interesting question and I think the jury is still out on whether
> >>the
> >>Linked List or ArrayList would perform better here - I have seen arguments
> >>going
> >>both ways (if I have some extra time I will run some benchmarks for our
> >>specific
> >>use). A lot depends on the size of the resultset and I would not use this
> >>method for running a query returning a really large number of rows anyway.
>
> >>That
> >>said, I'd be happy to change it if there definitely is a performace
> >>difference.
> >>
> >>Thomas
> >>
> >>
> >>Quoting Eduardo Issao Ito <zi...@su...>:
> >>
> >>
> >>>I noticed that JdbcHelper.queryForList() method returns an ArrayList, but
> a
> >>
> >>>LinkedList should not be more appropriate (more performant without need
> of
> >>>array
> >>>realocation as the list grows) as it is a generic funcition and the
> >>
> >>rowcount
> >>
> >>>is
> >>>not known in advance?
> >>>
> >>>
> >>>
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> >
> >
> >
> >
> >
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