Re: SQL help for efficient time handling..
От | Popeanga Marian |
---|---|
Тема | Re: SQL help for efficient time handling.. |
Дата | |
Msg-id | 3E7C22B8.70601@cnlo.ro обсуждение исходный текст |
Ответ на | SQL help for efficient time handling.. (Rajesh Kumar Mallah <mallah@trade-india.com>) |
Ответы |
Re: SQL help for efficient time handling..
(Rajesh Kumar Mallah <mallah@trade-india.com>)
|
Список | pgsql-sql |
Hello Mallah, Have you tryed this : SELECT time_id from time_dimension where sql_time=cast(now() as time without time zone); Your tabel is indexed for a time h:m:s and you should to have a where clause with a time value like this index is defined. Other way you will have a filter scan. Rajesh Kumar Mallah wrote: >Hi everyone, > >I have a table time_dimension loaded with 1440 records >i record for each min in 24 hrs > > >CREATE TABLE general.time_dimension >( > time_id integer not null , > sql_time time(0) without time zone not null, > PRIMARY KEY (time_id), > UNIQUE (sql_time) >); > >sample data is like, > >tradein_clients=# SELECT * from time_dimension limit 10; >+---------+----------+ >| time_id | sql_time | >+---------+----------+ >| 1 | 00:00:00 | >| 2 | 00:01:00 | >| 3 | 00:02:00 | >| 4 | 00:03:00 | >| 5 | 00:04:00 | >| 6 | 00:05:00 | >| 7 | 00:06:00 | >| 8 | 00:07:00 | >| 9 | 00:08:00 | >| 10 | 00:09:00 | >+---------+----------+ >(10 rows) > >To get current_time_id i use a query like >SELECT time_id from time_dimension where sql_time=date_trunc('minute' , cast(now() as time without time zone) ); > >it works but uses seq_scan >Seq Scan on time_dimension (cost=0.00..35.00 rows=5 width=4) (actual time=4.75..8.16 rows=1 loops=1) > Filter: ((sql_time)::interval = date_trunc('minute'::text, ((now())::time without time zone)::interval)) > Total runtime: 8.20 msec > >whereas a query like > >explain analyze SELECT time_id from time_dimension where sql_time='13:13:13'; >+------------------------------------------------------------------------------------------------------------------------------------------+ >| QUERY PLAN | >+------------------------------------------------------------------------------------------------------------------------------------------+ >| Index Scan using time_dimension_sql_time_key on time_dimension (cost=0.00..4.82 rows=1 width=4) (actual time=0.03..0.03rows=0 loops=1) | >| Index Cond: (sql_time = '13:13:13'::time without time zone) | >| Total runtime: 0.06 msec >-------------------------------------------------------------------------------------------------------------------------------------------- >take much less. > >can anyone tell be the best way to get time_id from time_dimension for current_time. > >any help is appreciated. > >Regds >Mallah. > > > > -- Popeanga Marian DBA Oracle CNLO Romania
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