Horton

Re: [HACKERS] WAL logging problem in 9.4.3?

Noah Misch <noah@leadboat.com>

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From: Noah Misch <noah@leadboat.com>
To: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: robertmhaas@gmail.com, pgsql-hackers@postgresql.org, 9erthalion6@gmail.com, andrew.dunstan@2ndquadrant.com, hlinnaka@iki.fi, michael@paquier.xyz
Date: 2019-12-08T18:09:51Z
Lists: pgsql-hackers 
I reviewed your latest code, and it's nearly complete.  mdimmedsync() syncs
only "active segments" (as defined in md.c), but smgrDoPendingSyncs() must
sync active and inactive segments.  This matters when mdtruncate() truncated
the relation after the last checkpoint, causing active segments to become
inactive.  In such cases, syncs of the inactive segments will have been queued
for execution during the next checkpoint.  Since we skipped the
XLOG_SMGR_TRUNCATE record, we must complete those syncs before commit.  Let's
just modify smgrimmedsync() to always sync active and inactive segments;
that's fine to do in other smgrimmedsync() callers, even though they operate
on relations that can't have inactive segments.

On Tue, Dec 03, 2019 at 08:51:46PM +0900, Kyotaro Horiguchi wrote:
> At Thu, 28 Nov 2019 17:23:19 -0500, Noah Misch <noah@leadboat.com> wrote in 
> > On Thu, Nov 28, 2019 at 09:35:08PM +0900, Kyotaro Horiguchi wrote:
> > > I measured the performance with the latest patch set.
> > > 
> > > > 1. Determine $DDL_COUNT, a number of DDL transactions that take about one
> > > >    minute when done via syncs.
> > > > 2. Start "pgbench -rP1 --progress-timestamp -T180 -c10 -j10".
> > > > 3. Wait 10s.
> > > > 4. Start one DDL backend that runs $DDL_COUNT transactions.
> > > > 5. Save DDL start timestamp, DDL end timestamp, and pgbench output.

>  wal_buffers                | 512

This value (4 MiB) is lower than a tuned production system would have.  In
future benchmarks (if any) use wal_buffers=2048 (16 MiB).

Commits

  1. Add perl2host call missing from a new test file.

  2. Skip WAL for new relfilenodes, under wal_level=minimal.

  3. Revert "Skip WAL for new relfilenodes, under wal_level=minimal."

  4. Back-patch log_newpage_range().

  5. During heap rebuild, lock any TOAST index until end of transaction.

  6. In log_newpage_range(), heed forkNum and page_std arguments.

  7. Back-patch src/test/recovery and PostgresNode from 9.6 to 9.5.

  8. Reduce pg_ctl's reaction time when waiting for postmaster start/stop.

  9. Accelerate end-of-transaction dropping of relations

  10. Redesign the planner's handling of index-descent cost estimation.

  11. Make TRUNCATE do truncate-in-place when processing a relation that was created