Re: Help with bulk read performance

От: Pierre C
Тема: Re: Help with bulk read performance
Дата: ,
Msg-id: op.vntbn2ujeorkce@apollo13
(см: обсуждение, исходный текст)
Ответ на: Re: Help with bulk read performance  (Dan Schaffer)
Ответы: Re: Help with bulk read performance  (Nick Matheson)
Список: pgsql-performance

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Help with bulk read performance  (Dan Schaffer, )
 Re: Help with bulk read performance  (Jim Nasby, )
 Re: Help with bulk read performance  (Andy Colson, )
  Re: Help with bulk read performance  (Jim Nasby, )
   Re: Help with bulk read performance  (Andy Colson, )
    Re: Help with bulk read performance  (Nick Matheson, )
    Re: Help with bulk read performance  (Dan Schaffer, )
     Re: Help with bulk read performance  ("Pierre C", )
      Re: Help with bulk read performance  (Nick Matheson, )
 Re: Help with bulk read performance  (Jim Nasby, )
 Re: Help with bulk read performance  (Krzysztof Nienartowicz, )

> If the data are stored as a byte array but retrieve into a ResultSet,
> the unpacking time goes up by an order of magnitude and the
> observed total throughput is 25 MB/s.  If the data are stored in a
> Postgres float array and unpacked into a byte stream, the
> observed throughput is 20 MB/s.


float <-> text conversions are very slow, this is in fact due to the
mismatch between base-2 (IEEE754) and base-10 (text) floating point
representation, which needs very very complex calculations.


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