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Re: [Bacula-devel] Alternative DB proposal

2008/10/14 Kern Sibbald <kern@xxxxxxxxxxx>:
> On Tuesday 14 October 2008 10:42:22 Yuri Timofeev wrote:
>> 2008/10/14 Kern Sibbald <kern@xxxxxxxxxxx>:
>> > On Tuesday 14 October 2008 10:06:22 Yuri Timofeev wrote:
>> >> 2008/10/14 Kern Sibbald <kern@xxxxxxxxxxx>:
>> >> > On Tuesday 14 October 2008 09:39:27 John Huttley wrote:
>> >> >> So the modified version is actually a bit faster?
>> >> >
>> >> > That is what I understood too, but I wanted to get a confirmation.
>> >> >
>> >> > If it is indeed the case that the new case runs faster, it is indeed
>> >> > odd, and I would say the tester has fallen into a very trap that is
>> >> > very common in performance analysis.
>> >>
>> >> Of course, this is only the first test!
>> >> I think that will soon be able to hold a series of tests.
>> >> I just limiting the number of entries from 10M to 5M (very long wait)
>> >
>> > Yes, clearly running something 10 times is not very practical if it takes
>> > 35 hours each time, so the test size must be reduced, and you can reduce
>> > the number of runs from 10 to say 5.
>> >
>> > However, what was not at all evident from your first post is that there
>> > are apparently subtle differences in schemas that I did not see and
>> > differences in the size of the data you were inserting -- and those could
>> > possibly explain a large (or even all)  the difference in timings.
>> In an alternative scheme appear new fields : size, ctime, mtime.
>> I therefore reduced length the value that is inserted into the field LStat.
>> For the old scheme, I used :
>> char *lstat = "MI s9MB IG0 B H2 H0 A 9t BAA I BIVsDs BIR93m BIVqaC A A E";
>> and for the new scheme:
>> char *lstat = "MI s9MB IG0 B H2 H0 A 9t BAA I";
>> But it is not entirely correct.
>> In an alternative scheme2 appear new fields : size, ctime, mtime, _atime_.
>> The new version of the tests, I did as correctly:
>> char *lstat = "MI s9MB IG0 B H2 H0 A 9t BAA I BIVsDs BIR93m BIVqaC A A
>> E"; /* for traditional scheme */
>> char *lstat    = "MI s9MB IG0 B H2 H0 A BAA I BIVsDs BIR93m BIVqaC";
>> /* for new scheme */
>> Therefore, in alternative scheme the length of lstat reduced.
>> That is right?
> I would not say it is a question of being right or not.  It is a possibility,
> but it would be a big effort to eliminate those fields -- first there is the
> programming problem of finding every place they are accessed and ensuring the
> new fields are used, but even more important, there is the problem of
> converting existing databases from the old scheme to the new one.

Yes, I agree.
Perhaps these studies will never be translated into bacula source code.
However, it is interesting.

with best regards

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