Horton

Re: WAL logging problem in 9.4.3?

Martijn van Oosterhout <kleptog@svana.org>

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From: Martijn van Oosterhout <kleptog@svana.org>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Fujii Masao <masao.fujii@gmail.com>, Andres Freund <andres@anarazel.de>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2015-07-03T17:14:26Z
Lists: pgsql-hackers 
On Fri, Jul 03, 2015 at 12:53:56PM -0400, Tom Lane wrote:
> Fujii Masao <masao.fujii@gmail.com> writes:
> > Okay, so probably we need to change WAL replay of TRUNCATE so that
> > the index file is truncated to one containing only meta page instead of
> > empty one. That is, the WAL replay of TRUNCATE would need to call
> > index_build() after smgrtruncate() maybe.
> 
> That seems completely unworkable.  For one thing, index_build would expect
> to be able to do catalog lookups, but we can't assume that the catalogs
> are in a good state yet.
> 
> I think the responsibility has to be on the WAL-writing end to emit WAL
> instructions that lead to a correct on-disk state.  Putting complex
> behavior into the reading side is fundamentally misguided.

Am I missing something. ISTM that if the truncate record was simply not
logged at all everything would work fine. The whole point is that the
table was created in this transaction and so if it exists the table on
disk must be the correct representation.

The broken index is just one symptom. The heap also shouldn't be
truncated at all. If you insert a row before commit then after replay
the tuple should be there still.

Have a nice day,
-- 
Martijn van Oosterhout   <kleptog@svana.org>   http://svana.org/kleptog/
> He who writes carelessly confesses thereby at the very outset that he does
> not attach much importance to his own thoughts.
   -- Arthur Schopenhauer

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