Re: Bitmap Heap scan 8.1/8.2 - Mailing list pgsql-general

From Martin Marques
Subject Re: Bitmap Heap scan 8.1/8.2
Date
Msg-id 471DE2DE.50201@bugs.unl.edu.ar
Whole thread Raw
In response to Re: Bitmap Heap scan 8.1/8.2  (Martin Marques <martin@bugs.unl.edu.ar>)
Responses Re: Bitmap Heap scan 8.1/8.2  ("Pavel Stehule" <pavel.stehule@gmail.com>)
Re: Bitmap Heap scan 8.1/8.2  (Alvaro Herrera <alvherre@commandprompt.com>)
List pgsql-general
Martin Marques escribió:
> Pavel Stehule wrote:
>>
>> try
>>
>> set work_mem to '8MB';
>> and
>> explain analyze select ..
>
> These things didn't help. What changed the plan completely was this:
>
> seq_page_cost = 5.0                     # measured on an arbitrary scale
> cpu_tuple_cost = 0.05                   # same scale as above

Can someone explain how this parameters are measured? What is 5.0 in
this case for seq_page_cost?

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