Horton

Re: Improving connection scalability: GetSnapshotData()

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Ian Barwick <ian.barwick@2ndquadrant.com>, Michael Paquier <michael@paquier.xyz>, 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: 2020-09-15T00:42:51Z
Lists: pgsql-hackers 
Hi,

On 2020-09-14 20:14:48 -0400, Tom Lane wrote:
> Andres Freund <andres@anarazel.de> writes:
> > I think the approach of having a long running psql session is really
> > useful, and probably would speed up some tests. Does anybody have a good
> > idea for how to best, and without undue effort, to integrate this into
> > PostgresNode.pm?  I don't really have a great idea, so I think I'd leave
> > it with a local helper in the new test?
> 
> You could use the interactive_psql infrastructure that already exists
> for psql/t/010_tab_completion.pl.  That does rely on IO::Pty, but
> I think I'd prefer to accept that dependency for such tests over rolling
> our own IPC::Run, which is more or less what you've done here.

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?

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