Re: WAL usage calculation patch

Justin Pryzby <pryzby@telsasoft.com>

From: Justin Pryzby <pryzby@telsasoft.com>

To: Julien Rouhaud <rjuju123@gmail.com>

Cc: Amit Kapila <amit.kapila16@gmail.com>, Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, Dilip Kumar <dilipbalaut@gmail.com>, Kuntal Ghosh <kuntalghosh.2007@gmail.com>, Fujii Masao <masao.fujii@oss.nttdata.com>, Kirill Bychik <kirill.bychik@gmail.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>, Thomas Munro <thomas.munro@gmail.com>

Date: 2020-04-18T20:41:05Z

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 →

Change the display of WAL usage statistics in Explain.
- 69bfaf2e1de4 13.0 landed
Cosmetic fixups for WAL usage work.
- ef08ca113fe3 13.0 landed
Allow parallel create index to accumulate buffer usage stats.
- 5c71362174eb 13.0 landed
- f179e9f01b65 11.8 landed
- 13823ad3b012 12.3 landed
Allow autovacuum to log WAL usage statistics.
- b7ce6de93b59 13.0 landed
Add the option to report WAL usage in EXPLAIN and auto_explain.
- 33e05f89c53e 13.0 landed
Allow pg_stat_statements to track WAL usage statistics.
- 6b466bf5f2be 13.0 landed
Add infrastructure to track WAL usage.
- df3b181499b4 13.0 landed
Include information on buffer usage during planning phase, in EXPLAIN output, take two.
- ce77abe63cfc 13.0 cited
Include information on buffer usage during planning phase, in EXPLAIN output.
- ed7a5095716e 13.0 cited
Allow parallel vacuum to accumulate buffer usage.
- 3a5e22138a8d 13.0 landed
Allow pg_stat_statements to track planning statistics.
- 17e03282241c 13.0 cited

On Sat, Apr 18, 2020 at 05:39:35PM +0200, Julien Rouhaud wrote:
> On Sat, Apr 18, 2020 at 6:16 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
> >
> > On Fri, Apr 17, 2020 at 6:45 PM Peter Eisentraut <peter.eisentraut@2ndquadrant.com> wrote:
> > > On 2020-04-14 05:57, Amit Kapila wrote:
> > > > Peter E, others, any suggestions on how to move forward?  I think here
> > > > we should follow the rule "follow the style of nearby code" which in
> > > > this case would be to have one space after each field as we would like
> > > > it to be closer to the "Buffers" format.  It would be good if we have
> > > > a unified format among all Explain stuff but we might not want to
> > > > change the existing things and even if we want to do that it might be
> > > > a broader/bigger change and we should do that as a PG14 change.  What
> > > > do you think?
> > >
> > > If looks like shortening to fpw= and using one space is the easiest way
> > > to solve this issue.
> > >
> >
> > I am fine with this approach and will change accordingly.  I will wait
> > for a few days (3-4 days) to see if someone shows up with either an
> > objection to this or with a better idea for the display of WAL usage
> > information.
> 
> That was also my preferred alternative.  PFA a patch for that.  I also
> changed to "fpw" for the non textual output for consistency.

Should capitalize at least the non-text one ?  And maybe the text one for
consistency ?

+               ExplainPropertyInteger("WAL fpw", NULL,                                                                                                                                              

And add the acronym to the docs:

$ git grep 'full page' '*/explain.sgml'
doc/src/sgml/ref/explain.sgml:      number of records, number of full page writes and amount of WAL bytes

"..full page writes (FPW).."

Should we also change vacuumlazy.c for consistency ?

+                                                        _("WAL usage: %ld records, %ld full page writes, "
+                                                          UINT64_FORMAT " bytes"),

-- 
Justin