Horton

Re: Improving connection scalability: GetSnapshotData()

Peter Geoghegan <pg@bowt.ie>

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From: Peter Geoghegan <pg@bowt.ie>
To: Andres Freund <andres@anarazel.de>
Cc: Robert Haas <robertmhaas@gmail.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>, Alexander Korotkov <a.korotkov@postgrespro.ru>, Alvaro Herrera <alvherre@2ndquadrant.com>, Jonathan Katz <jkatz@postgresql.org>, Bruce Momjian <bruce@momjian.us>, Thomas Munro <thomas.munro@gmail.com>, David Rowley <dgrowleyml@gmail.com>
Date: 2020-04-07T18:32:42Z
Lists: pgsql-hackers 
On Tue, Apr 7, 2020 at 11:28 AM Andres Freund <andres@anarazel.de> wrote:
> There is a lot of code that is pretty unsafe around wraparounds... They
> are getting easier and easier to hit on a regular schedule in production
> (plenty of databases that hit wraparounds multiple times a week). And I
> don't think we as PG developers often don't quite take that into
> account.

It would be nice if there was high level documentation on wraparound
hazards. Maybe even a dedicated README file.

-- 
Peter Geoghegan

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