Re: Substantial different index use between 9.5 and 9.6

От: Tom Lane
Тема: Re: Substantial different index use between 9.5 and 9.6
Дата: ,
Msg-id: 21406.1480636092@sss.pgh.pa.us
(см: обсуждение, исходный текст)
Ответ на: Substantial different index use between 9.5 and 9.6  (Bill Measday)
Ответы: Re: Substantial different index use between 9.5 and 9.6  (Bill Measday)
Список: pgsql-performance

Скрыть дерево обсуждения

Substantial different index use between 9.5 and 9.6  (Bill Measday, )
 Re: Substantial different index use between 9.5 and 9.6  (Tom Lane, )
  Re: Substantial different index use between 9.5 and 9.6  (Bill Measday, )
   Re: Substantial different index use between 9.5 and 9.6  (Daniel Blanch Bataller, )
    Re: Substantial different index use between 9.5 and 9.6  (Bill Measday, )

Bill Measday <> writes:
> Substantial different index use between 9.5 and 9.6

Maybe you missed an ANALYZE after migrating?  The plan difference
seems to be due to a vast difference in rowcount estimate for the
m_elevations condition:

>       ->  Bitmap Heap Scan on m_elevations e
> (cost=282802.21..37401439.43 rows=3512160 width=8)

>       ->  Seq Scan on m_elevations e
> (cost=10000000000.00..13296950520.12 rows=3512159563 width=8)

If you don't know where that factor-of-1000 came from, maybe take
it up with the postgis folk.  It'd mostly be coming out of their
selectivity estimation routines.

            regards, tom lane



В списке pgsql-performance по дате сообщения:

От: Bill Measday
Дата:
Сообщение: Re: Substantial different index use between 9.5 and 9.6
От: Daniel Blanch Bataller
Дата:
Сообщение: Re: Substantial different index use between 9.5 and 9.6