On Fri, Jan 6, 2017 at 2:38 PM, Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> table_size | indexes | parallel_degree | time
> ------------+---------+-----------------+----------
> 6.5GB | 0 | 1 | 00:00:14
> 6.5GB | 0 | 2 | 00:00:02
> 6.5GB | 0 | 4 | 00:00:02
Those numbers look highly suspect.
Are you sure you're not experiencing caching effects? (ie: maybe you
ran the second and third vacuums after the first, and didn't flush the
page cache, so the table was cached)
> 6.5GB | 2 | 1 | 00:02:18
> 6.5GB | 2 | 2 | 00:00:38
> 6.5GB | 2 | 4 | 00:00:46
...
> 13GB | 0 | 1 | 00:03:52
> 13GB | 0 | 2 | 00:00:49
> 13GB | 0 | 4 | 00:00:50
..
> 13GB | 2 | 1 | 00:12:42
> 13GB | 2 | 2 | 00:01:17
> 13GB | 2 | 4 | 00:02:12
These would also be consistent with caching effects
