Re: SQL help for efficient time handling..
От | Rajesh Kumar Mallah |
---|---|
Тема | Re: SQL help for efficient time handling.. |
Дата | |
Msg-id | 200303221425.02824.mallah@trade-india.com обсуждение исходный текст |
Ответ на | Re: SQL help for efficient time handling.. (Popeanga Marian <pmarian@cnlo.ro>) |
Список | pgsql-sql |
nopes! does not match any record.. SELECT time_id from time_dimension where sql_time=cast( now() as time without time zone); +---------+ | time_id | +---------+ +---------+ (0 rows) On Saturday 22 Mar 2003 2:15 pm, Popeanga Marian wrote: > 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 > > > > > -- Rajesh Kumar Mallah, Project Manager (Development) Infocom Network Limited, New Delhi phone: +91(11)6152172 (221) (L) ,9811255597 (M) Visit http://www.trade-india.com , India's Leading B2B eMarketplace.
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