Re: ANALYZE sampling is too good

On 12/08/2013 08:14 PM, Greg Stark wrote:
> The whole accounts table is 1.2GB and contains 10 million rows. As
> expected with rows_per_block set to 1 it reads 240MB of that
> containing nearly 2 million rows (and takes nearly 20s -- doing a full
> table scan for select count(*) only takes about 5s):

One simple thing we could do, without or in addition to changing the 
algorithm, is to issue posix_fadvise() calls for the blocks we're going 
to read. It should at least be possible to match the speed of a plain 
sequential scan that way.

- Heikki