On Thu, May 5, 2016 at 1:32 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> I've pushed a first cut at release notes for 9.6. There's a good deal
> of work to do yet:
>
> * The section about parallel query could probably stand to be fleshed out,
> but I'm unsure what to say. Somebody who's worked on that should provide
> some text.
>
> * Bruce usually likes to sprinkle the notes with a whole lot of links
> to the main docs. I've only bothered with links for new GUCs and system
> views.
>
> * As is somewhat customary for early drafts of the notes, I've made no
> attempt to call out which are the most significant changes. I've not
> tried to isolate the non-backwards-compatible items, either.
>
> Please review and comment before Monday, if you can.
As far as the parallel query stuff goes,
https://wiki.postgresql.org/wiki/Parallel_Query is a useful overview
of current restrictions which I'm still hoping to get incorporated
into the SGML documentation. I suggest revising the text to something
like this:
===
With 9.6, <productname>PostgreSQL</> introduces initial support for
parallel execution of large queries. Only strictly read-only queries
where the driving table is accessed via a sequential scan can be
parallelized. Hash joins and nested loops can be performed in
parallel, as can aggregation for supported aggregates. Much remains
to be done, but this is already a useful set of features.
===
If we put the documentation from that wiki page into the docs
someplace, then we could add a sentence "For an overview of the
current capabilities of parallel query, including relevant
restrictions, see <splat>."
I'd probably mention David Rowley as a third author on parallel query.
It's true that the great bulk of the development work and design over
the last few years was done by Amit and I, but parallel aggregate
resulted in several large patches that were entirely written by David.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company