Re: difficulties with time based queries

От: Tom Lane
Тема: Re: difficulties with time based queries
Дата: ,
Msg-id: 7371.1238981597@sss.pgh.pa.us
(см: обсуждение, исходный текст)
Ответ на: Re: difficulties with time based queries  ("Rainer Mager")
Ответы: Re: difficulties with time based queries  ("Rainer Mager")
Список: pgsql-performance

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difficulties with time based queries  ("Rainer Mager", )
 Re: difficulties with time based queries  (David Wilson, )
  Re: difficulties with time based queries  ("Rainer Mager", )
   Re: difficulties with time based queries  (Tom Lane, )
    Re: difficulties with time based queries  ("Rainer Mager", )
     Re: difficulties with time based queries  (Robert Haas, )
   Re: difficulties with time based queries  (Matthew Wakeling, )
 Re: difficulties with time based queries  (PFC, )
 Re: difficulties with time based queries  (Tom Lane, )
 Re: difficulties with time based queries  ("Rainer Mager", )
  Re: difficulties with time based queries  (PFC, )
   Re: difficulties with time based queries  (Nikolas Everett, )
 Re: difficulties with time based queries  ("Rainer Mager", )
  Re: difficulties with time based queries  (Tom Lane, )

"Rainer Mager" <> writes:
>> From: Tom Lane [mailto:]
>> Hmm ... it's pretty unusual to see the index fetch portion of a bitmap
>> scan take the bulk of the runtime.  Usually that part is fast and where
>> the pain comes is in fetching from the heap.   I wonder whether that
>> index has become bloated.  How big are the table and the index
>> physically?  (Look at pg_class.relpages, or if you want a really
>> accurate number try pg_relation_size().)

> Can you give me some more info on how to look at these stats?

Since you've got 8.3 it's easy: select pg_relation_size('tablename')
(or indexname).  The result is in bytes, so you might want to
divide by 1K or 1M to keep the number readable.

            regards, tom lane


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