[Maria-developers] eq_range_index_dives_limit
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 -- Sergei Petrunia, Software Developer MariaDB Corporation | Skype: sergefp | Blog: http://s.petrunia.net/blog
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-s.... 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
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 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-s.... 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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participants (3)
-
Ian Gilfillan -
Sergey Petrunia -
Varun Gupta