| From: | Simon Riggs <simon(dot)riggs(at)2ndquadrant(dot)com> |
|---|---|
| To: | Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com> |
| Cc: | Claudio Freire <klaussfreire(at)gmail(dot)com>, Peter Geoghegan <pg(at)bowt(dot)ie>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Faster inserts with mostly-monotonically increasing values |
| Date: | 2018-03-14 11:23:29 |
| Message-ID: | CANP8+jJg6DdNY41K-1Q9KE9Fxpc5CjzdLbJi0z8F1wOZoOwx+Q@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 14 March 2018 at 04:36, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com> wrote:
> I wonder if the shortened code path actually leads to
> heavier contention for EXCLUSIVE lock on the rightmost page, which in turn
> causes the slowdown. But that's just a theory. Any ideas how to prove or
> disprove that theory or any other pointers?
Certainly: dropping performance with higher sessions means increased
contention is responsible. Your guess is likely correct.
Suggest making the patch attempt a ConditionalLock on the target
block, so if its contended we try from top of index. So basically only
attempt the optimization if uncontended. This makes sense because in
many cases if the block is locked it is filling up and the RHS block
is more likely to change anyway.
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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