can a conditions_for_collection makes department to load each time?
but it has no sense.
Here is listing from the top of action processing if it helps. As an
autientication system I use devise. And dept_head user belongs to
department. But I think it should'n be checked on each row.
Processing DeptHead::TeachingPlacesController#index (for 127.0.0.1 at
2010-09-17 19:09:40) [GET]
DeptHead Load (3.5ms) SELECT * FROM "users" WHERE ("users"."id" =
4) AND ( ("users"."type" = 'DeptHead' ) ) LIMIT 1
Department Load (43.8ms) SELECT * FROM "departments" WHERE
("departments"."id" = 1)
SQL (99.3ms) SELECT count(DISTINCT "teaching_places".id) AS
count_all FROM "teaching_places" LEFT OUTER JOIN "lecturers" ON
"lecturers".id = "teaching_places".lecturer_id LEFT OUTER JOIN
"positions" ON "positions".id = "teaching_places".position_id WHERE
(("teaching_places"."department_id" = 1))
TeachingPlace Load (4.7ms) SELECT "teaching_places".* FROM
"teaching_places" WHERE (("teaching_places"."department_id" = 1))
ORDER BY "teaching_places"."id" ASC LIMIT 30 OFFSET 0
Lecturer Load (3.7ms) SELECT * FROM "lecturers" WHERE
("lecturers"."id" IN
(11,6,7,12,8,13,9,14,15,16,17,1,2,18,19,3,10,4,5))
Position Load (1.7ms) SELECT * FROM "positions" WHERE
("positions"."id" IN (1,2,3))
Rendering template within layouts/application
Rendering list
Rendered _list_header (26.4ms)
Rendered _list_column_headings (35.9ms)
Rendered _messages (2.4ms)
Rendered _list_messages (186.4ms)
Rendered _list_record_columns (12.6ms)
CACHE (0.0ms) SELECT * FROM "departments" WHERE ("departments"."id" = 1)
Rendered _list_actions (75.7ms)
Rendered _list_record (121.6ms)
Rendered _list_record_columns (4.4ms)
CACHE (0.0ms) SELECT * FROM "departments" WHERE ("departments"."id" = 1)
...
2010/9/17 Sergio Cambra .:: entreCables S.L. ::. <[email protected]>:
> On Viernes, 17 de Septiembre de 2010 01:29:30 Andrey Voronkov escribió:
>> This is an example of N+1 error in my case:
>>
>> ...
>>
>> CACHE (0.0ms) SELECT * FROM "departments" WHERE ("departments"."id" = 1)
>> Rendered _list_actions (26.8ms)
>> Rendered _list_record (34.9ms)
>> Rendered _list_record_columns (4.4ms)
>> CACHE (0.0ms) SELECT * FROM "departments" WHERE ("departments"."id" =
>> 1) Rendered _list_actions (26.9ms)
>> Rendered _list_record (33.4ms)
>> Rendered _list_record_columns (4.3ms)
>> CACHE (0.0ms) SELECT * FROM "departments" WHERE ("departments"."id" =
>> 1)
>
> If you are excluding department column, why is department loaded? Is it used
> in some override? In a security check? Anyway you can override
> active_scaffold_includes:
> def active_scaffold_includes
> �...@active_scaffold_includes ||= [:department]
> end
>
>
>>
>> ...
>>
>> 2010/9/17 Andrey Voronkov <[email protected]>:
>> > I have model TeachingPlace that belongs to Department and to the
>> > Lecturer models and has table field called position.
>> > I want to rid off N+1 SQL requests. There is no N+1 if
>> > config.columns = [:lecturer, :department, :position]
>> >
>> > Person who works with this interface is a department agent so I have
>> > this two methods:
>> >
>> > protected
>> >
>> > def before_create_save(record)
>> > if dept = current_dept_head.department
>> > record.department_id = dept.id
>> > end
>> > end
>> >
>> > def conditions_for_collection
>> > if @dept ||= current_dept_head.department
>> > {:department_id => @dept.id}
>> > else
>> > {:department_id => nil}
>> > end
>> > end
>> >
>> > As you can guess I do not need to display department field in list or
>> > anywhere in this interface because the user knows what department he
>> > represents. But this:
>> > config.list.columns.exclude :department
>> > causes N+1 error. Is there any kind of descision of my trouble?
>
> --
> Sergio Cambra .:: entreCables S.L. ::.
> Mariana Pineda 23, 50.018 Zaragoza
> T) 902 021 404 F) 976 52 98 07 E) [email protected]
>
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