Re: REINDEX : new parameter to preserve current average leaf density as new implicit FILLFACTOR

Thanks Peter

> From: Peter Geoghegan <pg(at)bowt(dot)ie>
> Sent: July 8, 2019 1:39 PM
> Subject: Re: REINDEX : new parameter to preserve current average leaf density as new implicit FILLFACTOR
>
> Perhaps you didn't take deleted_pages into account -- there must be
> free space that is reusable by the index that has yet to be reused.
> It would probably make sense to subtract that across the board.
>

Correct, I did not, but will do so for the next runs.

>
> I don't think that a test case that runs VACUUM when there are only
> 4300 deletions and 4300 insertions is particularly realistic, in
> general. You might see a larger difference if there was more churn
> between each VACUUM run.
>

Actually the test workload does not run any explicit VACUUM command,
it relies on autovacuum with these settings
(same settings for 9.4 and 12beta2)

autovacuum | on |
autovacuum_analyze_scale_factor | 0.4 |
autovacuum_analyze_threshold | 50000 |
autovacuum_max_workers | 6 |
autovacuum_naptime | 20 | s
autovacuum_vacuum_cost_delay | 0 | ms
autovacuum_vacuum_cost_limit | 9999 |
autovacuum_vacuum_scale_factor | 0 |
autovacuum_vacuum_threshold | 2000 |
autovacuum_work_mem | 1048576 | kB

To correspond to your " more churn between each VACUUM"
Would you then suggest increasing
autovacuum_vacuum_cost_delay and/or autovacuum_vacuum_scale_factor?

Cheers, John Lumby