Horton

Re: WAL logging problem in 9.4.3?

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Fujii Masao <masao.fujii@gmail.com>, Martijn van Oosterhout <kleptog@svana.org>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2015-07-09T18:23:15Z
Lists: pgsql-hackers 
On 2015-07-06 11:49:54 -0400, Tom Lane wrote:
> One idea I had was to allow the COPY optimization only if the heap file is
> physically zero-length at the time the COPY starts.  That would still be
> able to optimize in all the cases we care about making COPY fast for.
> Rather than reverting cab9a0656c36739f, which would re-introduce a
> different performance problem, perhaps we could have COPY create a new
> relfilenode when it does this.  That should be safe if the table was
> previously empty.

I'm not convinced that cab9a0656c36739f needs to survive in that
form. To me only allowing one COPY to benefit from the wal_level =
minimal optimization has a significantly higher cost than
cab9a0656c36739f.

My tentative guess is that the best course is to

a) Make heap_truncate_one_rel() create a new relfeilnode. That fixes the
   truncation replay issue.

b) Force new pages to be used when using the heap_sync mode in
   COPY. That avoids the INIT danger you found. It seems rather
   reasonable to avoid using pages that have already been the target of
   WAL logging here in general.

Andres

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