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Re: [Springframework-developer] JdbcHelper
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From: Eduardo I. I. <zi...@su...> - 2004-02-27 22:18:58
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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.
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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