AW: Strange query execution time

Поиск
Список
Период
Сортировка
От Zeugswetter Andreas SB
Тема AW: Strange query execution time
Дата
Msg-id 11C1E6749A55D411A9670001FA687963368361@sdexcsrv1.f000.d0188.sd.spardat.at
обсуждение исходный текст
Ответы Re: AW: Strange query execution time  (Tom Lane <tgl@sss.pgh.pa.us>)
Список pgsql-hackers
> Can  someone explain why the following query takes  1 second when using 
> LIKE and takes 30 seconds when replacing LIKE by = in the WHERE ? 

Because there is no optimization built in, that notices, that your
string does not contain a wildcard and would translate the restriction 
correspondingly. It is currently executed more or less like below:(I3.nameInfluence >= 'inf_vitesse' and
I3.nameInfluence< 'inf_vitessf'     and I3.nameInfluence LIKE  'inf_vitesse')
 
I already wanted to try to add this optimization myself, but lacked the time so far.
Anybody want to volunteer ?

TODO: add LIKE optimization to use = if constant does not contain any wildcards

Andreas


В списке pgsql-hackers по дате отправления:

Предыдущее
От: Tatsuo Ishii
Дата:
Сообщение: Re: stuck spin lock with many concurrent users
Следующее
От: Zeugswetter Andreas SB
Дата:
Сообщение: AW: Re: Backup and Recovery