Re: Bitmap Heap scan 8.1/8.2

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?