On 2019-05-13 09:47, David Rowley wrote:
> On Mon, 13 May 2019 at 03:28, Jonathan S. Katz <jkatz(at)postgresql(dot)org>
> wrote:
>> - Performance, e.g. enhanced partition pruning, COPY performance,
>> ATTACH
>
> I don't think it's very accurate to say that the performance of
> partition pruning has been improved. Really the improvement there is
> due to the change in the order of operations, where we now perform
> pruning before fetching partition meta-data. Pruning itself, I don't
> believe became any faster in PG12. There were, however various tweaks
> to improve performance of some operations around run-time partition
> pruning both in the planner and during execution, these, however, are
> not improvements to pruning itself, but more the operations around
> setting up pruning and handling what happens after pruning takes
> place. Bruce has now changed the release notes to mention "Improve
> performance of many operations on partitioned tables", which seems
> like a more accurate generalisation of what was improved, although, I
> still think it's overly vague.
Sounds like "partition pruning is now more efficient". eg less memory
usage (?), with a side effect of better performance leading from that
(?)