Re: WIP: Avoid creation of the free space map for small tables

Поиск
Список
Период
Сортировка
От Amit Kapila
Тема Re: WIP: Avoid creation of the free space map for small tables
Дата
Msg-id CAA4eK1L4ySv71_pg=kDeVqVkk9ijCoR_W+DgOiWLSX+4kbTqig@mail.gmail.com
обсуждение исходный текст
Ответ на Re: WIP: Avoid creation of the free space map for small tables  (John Naylor <john.naylor@2ndquadrant.com>)
Ответы Re: WIP: Avoid creation of the free space map for small tables  (John Naylor <john.naylor@2ndquadrant.com>)
Список pgsql-hackers
On Mon, Feb 11, 2019 at 10:48 PM John Naylor
<john.naylor@2ndquadrant.com> wrote:
>
> On 2/9/19, Amit Kapila <amit.kapila16@gmail.com> wrote:
> > On Tue, Feb 5, 2019 at 3:25 PM John Naylor <john.naylor@2ndquadrant.com>
> > wrote:
> >>
> >> On Tue, Feb 5, 2019 at 4:04 AM Amit Kapila <amit.kapila16@gmail.com>
> >> wrote:
> > This is certainly a good test w.r.t code coverage of new code, but I
> > have few comments:
> > 1. The size of records in test still depends on alignment (MAXALIGN).
> > Though it doesn't seem to be a problematic case, I still suggest we
> > can avoid using records whose size depends on alignment.  If you
> > change the schema as CREATE TABLE fsm_check_size (num1 int, num2 int,
> > str text);, then you can avoid alignment related issues for the
> > records being used in test.
>
> Done.
>

Oops, on again carefully studying the test, I realized my above
comment was wrong.  Let me explain with a test this time:
CREATE TABLE fsm_check_size (num int, str text);
INSERT INTO fsm_check_size SELECT i, rpad('', 1024, 'a') FROM
generate_series(1,3) i;

So here you are inserting 4-byte integer and 1024-bytes variable
length record.  So the tuple length will be tuple_header (24-bytes) +
4-bytes for integer + 4-bytes header for variable length data + 1024
bytes of actual data.  So, the length will be 1056 which is already
MAXALIGN.  I took the new comments added in your latest version of the
patch and added them to the previous version of the patch.   Kindly
see if I have not missed anything while merging the patch-versions?

-- 
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com

Вложения

В списке pgsql-hackers по дате отправления:

Предыдущее
От: "Nagaura, Ryohei"
Дата:
Сообщение: RE: Timeout parameters
Следующее
От: Kyotaro HORIGUCHI
Дата:
Сообщение: Re: shared-memory based stats collector