Horton

Re: First draft of PG 17 release notes

Bruce Momjian <bruce@momjian.us>

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From: Bruce Momjian <bruce@momjian.us>
To: David Rowley <dgrowleyml@gmail.com>
Cc: Melanie Plageman <melanieplageman@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2024-05-15T02:06:17Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Revert support for ALTER TABLE ... MERGE/SPLIT PARTITION(S) commands

  2. When creating materialized views, use REFRESH to load data.

  3. Revert temporal primary keys and foreign keys

  4. Avoid needless large memcpys in libpq socket writing

  5. Enhance nbtree ScalarArrayOp execution.

  6. Introduce a non-recursive JSON parser

  7. Combine freezing and pruning steps in VACUUM

  8. Allow SIGINT to cancel psql database reconnections.

  9. Provide API for streaming relation data.

  10. Add hash support functions and hash opclass for contrib/ltree.

  11. Pull up ANY-SUBLINK with the necessary lateral support.

  12. Read WAL directly from WAL buffers.

  13. Introduce the dynamic shared memory registry.

  14. Add macros for looping through a List without a ListCell.

  15. Support +/- infinity in the interval data type.

  16. Extend ALTER OPERATOR to allow setting more optimization attributes.

  17. Consider cheap startup paths in add_paths_to_append_rel

On Wed, May 15, 2024 at 02:03:32PM +1200, David Rowley wrote:
> On Wed, 15 May 2024 at 13:00, Bruce Momjian <bruce@momjian.us> wrote:
> >
> > On Tue, May 14, 2024 at 03:39:26PM -0400, Melanie Plageman wrote:
> > > "Reduce system calls by automatically merging reads up to io_combine_limit"
> >
> > Uh, as I understand it, the reduced number of system calls is not the
> > value of the feature, but rather the ability to request a larger block
> > from the I/O subsystem.  Without it, you have to make a request and wait
> > for each request to finish.  I am open to new wording, but I am not sure
> > your new wording is accurate.
> 
> I think you have the cause and effect backwards. There's no advantage
> to reading 128KB if you only need 8KB.  It's the fact that doing
> *larger* reads allows *fewer* reads that allows it to be more
> efficient.  There are also the efficiency gains from fadvise
> POSIX_FADV_WILLNEED. I'm unsure how to jam that into a short sentence.
> Maybe; "Optimize reading of tables by allowing pages to be prefetched
> and read in chunks up to io_combine_limit", or a bit more buzzy;
> "Optimize reading of tables by allowing pages to be prefetched and
> performing vectored reads in chunks up to io_combine_limit".

Yes, my point is that it is not the number of system calls or system
call overhead that is the advantage of this patch, but the ability to
request more of the I/O system in one call, which is not the same as
system calls.

I can use your wording, but how much prefetching to we enable now?

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  Only you can decide what is important to you.