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

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