Hi,
On 07/09/2015 05:00 PM, Michael Widenius wrote:
Hi!
Hi Igor,
I noticed that during Item_cond::fix_fields() and
Item_func_between::fix_fields() update these optimizer
related SELECT_LEX members:
thd->lex->current_select->cond_count and
thd->lex->current_select->between_count
The purpose of these members is to allocate optimizer related buffers
in:
- update_ref_and_keys() in sql_select.cc and
- check_func_dependency() in opt_table_elimination,cc
and it seems they have no any other purposes..
Correct.
From my understanding, this is a dead code and the collected values are
never used:
- cond_count and_between_count are later always initialized to 0
before the walk(count_sargable_conds) call in update_ref_and_keys().
And the call to check_func_dependency() is done after this call.
- moreover, using the values collected during fix_fields() would not be
correct to allocate optimized related buffers, because the code
in fix_fields() does not distinguish between different query parts,
so the items can be just a part of the SELECT list rather than a
part of WHERE/HAVING/ON.
This would note be a problem as the count was supposed to be an upper bound.
As it's not normal that you have many IF or BETWEEN in the SELECT
part, this was not a problem.
I looked at the patch and it's ok to commit.
Thanks. I created a bug report, for reference:
MDEV-8456 Dead code in Item_cond::fix_fields() and
Item_func_between::fix_fields()
and pushed into 10.1.
Regards,
Monty
_______________________________________________
Mailing list: https://launchpad.net/~maria-developers
Post to : [email protected]
Unsubscribe : https://launchpad.net/~maria-developers
More help : https://help.launchpad.net/ListHelp
