Horton

Re: Improving connection scalability: GetSnapshotData()

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Michael Paquier <michael@paquier.xyz>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Ian Barwick <ian.barwick@2ndquadrant.com>, Robert Haas <robertmhaas@gmail.com>, Thomas Munro <thomas.munro@gmail.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, Daniel Gustafsson <daniel@yesql.se>, "Jonathan S. Katz" <jkatz@postgresql.org>, Alexander Korotkov <a.korotkov@postgrespro.ru>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>, Peter Geoghegan <pg@bowt.ie>, Bruce Momjian <bruce@momjian.us>, David Rowley <dgrowleyml@gmail.com>
Date: 2020-09-15T03:03:34Z
Lists: pgsql-hackers 
Hi,

On 2020-09-15 11:56:24 +0900, Michael Paquier wrote:
> On Mon, Sep 14, 2020 at 05:42:51PM -0700, Andres Freund wrote:
> > My test uses IPC::Run - although I'm indirectly 'use'ing, which I guess
> > isn't pretty. Just as 013_crash_restart.pl already did (even before
> > psql/t/010_tab_completion.pl). I am mostly wondering whether we could
> > avoid copying the utility functions into multiple test files...
> > 
> > Does IO::Pty work on windows? Given that currently the test doesn't use
> > a pty and that there's no benefit I can see in requiring one, I'm a bit
> > hesitant to go there?
> 
> Per https://metacpan.org/pod/IO::Tty:
> "Windows is now supported, but ONLY under the Cygwin environment, see
> http://sources.redhat.com/cygwin/."
> 
> So I would suggest to make stuff a soft dependency (as Tom is
> hinting?), and not worry about Windows specifically.  It is not like
> what we are dealing with here is specific to Windows anyway, so you
> would have already sufficient coverage.  I would not mind if any
> refactoring is done later, once we know that the proposed test is
> stable in the buildfarm as we would get a better image of what part of
> the facility overlaps across multiple tests.

I'm confused - the test as posted should work on windows, and we already
do this in an existing test (src/test/recovery/t/013_crash_restart.pl). What's
the point in adding a platforms specific dependency here?

Greetings,

Andres Freund

Commits

  1. Try to unbreak 021_row_visibility.pl on mingw.

  2. Fix and test snapshot behavior on standby.

  3. Fix race condition in snapshot caching when 2PC is used.

  4. snapshot scalability: cache snapshots using a xact completion counter.

  5. Fix use of wrong index in ComputeXidHorizons().

  6. Make vacuum a bit more verbose to debug BF failure.

  7. snapshot scalability: Introduce dense array of in-progress xids.

  8. snapshot scalability: Move PGXACT->vacuumFlags to ProcGlobal->vacuumFlags.

  9. snapshot scalability: Move subxact info to ProcGlobal, remove PGXACT.

  10. snapshot scalability: Move PGXACT->xmin back to PGPROC.

  11. snapshot scalability: Don't compute global horizons while building snapshots.

  12. BRIN: Handle concurrent desummarization properly

  13. Track latest completed xid as a FullTransactionId.

  14. Rename VariableCacheData.nextFullXid to nextXid.

  15. snapshot scalability: Move delayChkpt from PGXACT to PGPROC.

  16. Report progress of CREATE INDEX operations