On 23.08.2016 15:41, Michael Paquier wrote:
On Tue, Aug 23, 2016 at 8:02 PM, Masahiko Sawada <sawada.m...@gmail.com> wrote:
As for PoC, I implemented parallel vacuum so that each worker
processes both 1 and 2 phases for particular block range.
Suppose we vacuum 1000 blocks table with 4 workers, each worker
processes 250 consecutive blocks in phase 1 and then reclaims dead
tuples from heap and indexes (phase 2).
So each worker is assigned a range of blocks, and processes them in
parallel? This does not sound performance-wise. I recall Robert and
Amit emails on the matter for sequential scan that this would suck
performance out particularly for rotating disks.
Rotating disks is not a problem - you can always raid them and etc. 8k
allocation per relation once per half an hour that is the problem. Seq
scan is this way = random scan...
Alex Ignatov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
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