maria-developers team mailing list archive

[Alexander Barkov <bar@xxxxxxxxxxx>]

Hi Sanja and Igor,


Can you please help to understand this pieces of code in sql_select.cc
in 10.0:


>   else if (cond->type() == Item::FUNC_ITEM ||
>            cond->real_item()->type() == Item::FIELD_ITEM)
>   {

It seems that the "cond->real_item()->type() == Item::FIELD_ITEM" part
of this condition is a dead code.


I added a DBUG_ASSERT in the very beginning of this block, like this:

>   else if (cond->type() == Item::FUNC_ITEM ||
>            cond->real_item()->type() == Item::FIELD_ITEM)
>   {
>     DBUG_ASSERT(cond->real_item()->type() != Item::FIELD_ITEM);


and run all tests. Nothing crashed.



I suspect that the following scenario could happen:


1. In April 2011 Igor fixed bugs #717577, #724942 with this commit:

> commit 8d9dd21d85e257051b45b2f779dcd9bf696bf9e1
> Author:	Igor Babaev <igor@xxxxxxxxxxxx>  Wed Apr 27 06:58:41 2011
> Committer:	Igor Babaev <igor@xxxxxxxxxxxx>  Wed Apr 27 06:58:41 2011
>
> Fixed LP bugs #717577, #724942.

and this line was probably to handle conditions like "WHERE field".



2. In July 2011 Sanja introduced a new function normalize_cond(),
with this commit:

> commit 20a2e1d0ac46e375ee7246576b541624c6f8f028
> Author:	unknown <sanja@xxxxxxxxxxxx>  Thu Jul 21 11:20:55 2011
> unknown <sanja@xxxxxxxxxxxx>  Thu Jul 21 11:20:55 2011

so all conditions "WHERE/HAVING field" are now replaced
to "WHERE/HAVING field<>0".


So now, by the time of a build_equal_items_for_cond() call
all conditions are already replaced and no FIELD_ITEM are
actually possible.


Can you please confirm this?



If my guess is correct then this part can now be safely removed:

>            ||
>            cond->real_item()->type() == Item::FIELD_ITEM




Thanks.