Re: Bitmap Heap scan 8.1/8.2

From: Martin Marques <martin(at)bugs(dot)unl(dot)edu(dot)ar>
To: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Bitmap Heap scan 8.1/8.2
Date: 2007-10-23 12:02:38
Message-ID: 471DE2DE.50201@bugs.unl.edu.ar
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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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