Horton

Re: [Proposal] Fully WAL logged CREATE DATABASE - No Checkpoints

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Andres Freund <andres@anarazel.de>, Dilip Kumar <dilipbalaut@gmail.com>, Ashutosh Sharma <ashu.coek88@gmail.com>, Maciek Sakrejda <m.sakrejda@gmail.com>, Bruce Momjian <bruce@momjian.us>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Andrew Dunstan <andrew@dunslane.net>, Heikki Linnakangas <hlinnaka@iki.fi>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2022-03-29T19:20:17Z
Lists: pgsql-hackers 
On Tue, Mar 29, 2022 at 2:37 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
> > On Tue, Mar 29, 2022 at 2:17 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> >> it's some random algorithm that they probably feel at liberty
> >> to change.
>
> > I guess that characterization surprises me. The man page for
> > getopt_long() says this, and has for a long time at least on systems
> > I've used:
>
> Yeah, they say they follow the POSIX spec when you set POSIXLY_CORRECT.
> What they don't spell out in any detail is what they do when you don't.
> We know that it involves rearranging the argv[] array behind the
> application's back, but not what the rules are for doing that.  In
> particular, they must have some undocumented and probably not very safe
> method for deciding which arguments are neither switches nor switch
> arguments.

I mean, I think of an option as something that starts with '-'. The
documentation contains a caveat that says: "The special argument ‘--’
forces in all cases the end of option scanning." So I think I would
expect it just looks for arguments starting with '-' that do not
follow an argument that is exactly "--".

<looks around for the source code>

https://github.com/gcc-mirror/gcc/blob/master/libiberty/getopt.c

   If an element of ARGV starts with '-', and is not exactly "-" or "--",
   then it is an option element.  The characters of this element
   (aside from the initial '-') are option characters.  If `getopt'
   is called repeatedly, it returns successively each of the option characters
   from each of the option elements.

OK - so I was off slightly. Either "-" or "--" terminates the options
list. Apart from that anything starting with "-" is an option.

I think you're overestimating the level of mystery that's present
here, as well as the likelihood that the rules could ever be changed.

-- 
Robert Haas
EDB: http://www.enterprisedb.com

Commits

  1. When using the WAL-logged CREATE DATABASE strategy, bulk extend.

  2. Avoid using a fake relcache entry to own an SmgrRelation.

  3. Fix data-corruption hazard in WAL-logged CREATE DATABASE.

  4. initdb: When running CREATE DATABASE, use STRATEGY = WAL_COPY.

  5. Simplify a needlessly-complicated regular expression.

  6. In 020_createdb.pl, change order of command-line arguments.

  7. Add new block-by-block strategy for CREATE DATABASE.

  8. Fix replay of create database records on standby

  9. Refactor code for reading and writing relation map files.

  10. Replace RelationOpenSmgr() with RelationGetSmgr().

  11. Refactor the fsync queue for wider use.