Re: Why DISTINCT ... DESC is slow?

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От Ron Johnson
Тема Re: Why DISTINCT ... DESC is slow?
Дата
Msg-id 457ECAB0.9050306@cox.net
обсуждение исходный текст
Ответ на Why DISTINCT ... DESC is slow?  (Anton <anton200@gmail.com>)
Ответы Re: Why DISTINCT ... DESC is slow?  (Erik Jones <erik@myemma.com>)
Re: Why DISTINCT ... DESC is slow?  (Anton <anton200@gmail.com>)
Список pgsql-general
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On 12/12/06 01:28, Anton wrote:
> Hi. With this table (about 800 000 rows):
>
> =# \d n_traffic
>                         Table "public.n_traffic"
>    Column    |            Type             |          Modifiers
> --------------+-----------------------------+------------------------------
> login_id     | integer                     | not null
> traftype_id  | integer                     | not null
> collect_time | timestamp without time zone | not null default now()
> bytes_in     | bigint                      | not null default (0)::bigint
> bytes_out    | bigint                      | not null default (0)::bigint
> Indexes:
>    "n_traffic_collect_time" btree (collect_time)
>    "n_traffic_login_id" btree (login_id)
>    "n_traffic_login_id_collect_time" btree (login_id, collect_time)
> Foreign-key constraints:
>    "n_traffic_login_id_fkey" FOREIGN KEY (login_id) REFERENCES
> n_logins(login_id) ON UPDATE CASCADE
>    "n_traffic_traftype_id_fkey" FOREIGN KEY (traftype_id) REFERENCES
> n_traftypes(traftype_id) ON UPDATE CASCADE

Why do you have indexes on both LOGIN_ID *and* LOGIN_ID + COLLECT_TIME?

ISTM that you can drop the LOGIN_ID index.

- --
Ron Johnson, Jr.
Jefferson LA  USA

Is "common sense" really valid?
For example, it is "common sense" to white-power racists that
whites are superior to blacks, and that those with brown skins
are mud people.
However, that "common sense" is obviously wrong.
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