maria-developers team mailing list archive

[Varun Gupta <varungupta1803@xxxxxxxxx>]

Hi Ian,
The task was mainly to set a value greater than 0. So on the optimizer call
it was decided that we can raise it to 200 too. I will do it in a new patch.

On Sat 2 Feb, 2019, 12:36 AM Ian Gilfillan <ian@xxxxxxxxxxx wrote:

> I see the eq_range_index_dive_limit default has been set to 10 in
> 10.4.3. I see some different EXPLAIN results in the commit, but I don't
> see any notes on why or how 10 was chosen over any other value. MySQL
> increased the default to 200 from MySQL 5.7.4, based it seems on some
> community feedback that 10 was too low, for example:
>
> https://www.facebook.com/notes/mysql-at-facebook/eq_range_index_dive_limit-system-variable-in-mysql-56/10151533648715933.
>
> What was the thinking behind choosing 10 as the new default?
>
> On 2018/10/12 12:58, Sergey Petrunia wrote:
> > Hello,
> >
> > So, MDEV-16934 introduced eq_range_index_dives_limit into 10.2.8 and
> 10.3.0.
> >
> > The default was set to 0 (which means no limit) in order to not introduce
> > optimizer behavior change into stable versions.
> >
> > The question is: should 10.4 also have 0 by default or we can set it to
> some
> > finite limit? MySQL's default value is 10.
> >
> > BR
> >   Sergei
>
>
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