Re: pgsql: docs: fist draft version of the PG 12 release notes

On 2019/05/10 5:57, Bruce Momjian wrote:
> So, in this case, there were so many partitioning improvements, I just
> lumped them into one item. I think everyone can consider partitions to
> perform much better in PG 12. Is there something more specific we
> should communicate here?

So the current text, which is:

+<para>
+Improve performance of pruning many partitions (Amit Langote, David
Rowley, Tom Lane, Álvaro Herrera)
+</para>
+
+<para>
+Now thousands of partitions can be pruned efficiently.
+</para>
+</listitem>

mentions improving "pruning" efficiency which applies only to
SELECT/UPDATE/DELETE queries and can be attributed to only one of the many
commits listed with this item. Performance of short INSERTs (as opposed
to bulk-inserts including COPY) is also improved, but it has nothing to do
"pruning".

That said, efficiency is improved in both cases by not doing redundant
work for partitions that are not affected by the query, that is,

* for partitions which are pruned for a given SELECT/UPDATE/DELETE query
(planner improvement)

* for partitions which are not inserted into by a given INSERT statement
(executor improvement, part of which was done in v11 but v11 still locks
*all* partitions whereas v12 will only lock those that are inserted into)

So, it might be fair to lump them, but maybe not use the word "pruning",
because it describes only subset of affected workloads.

Does that help?

Thanks,
Amit