Horton

Re: Add pg_walinspect function with block info columns

Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>

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From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
To: Peter Geoghegan <pg@bowt.ie>
Cc: Michael Paquier <michael@paquier.xyz>, Melanie Plageman <melanieplageman@gmail.com>, Matthias van de Meent <boekewurm+postgres@gmail.com>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2023-03-17T07:20:09Z
Lists: pgsql-hackers

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On Fri, Mar 17, 2023 at 7:33 AM Peter Geoghegan <pg@bowt.ie> wrote:
>
> > IIUC, the concern raised so far in this thread is not just on the
> > performance of JOIN queries to get both block info and record level
> > info, but on ease of using pg_walinspect functions. If
> > pg_get_wal_block_info emits the record level information too (which
> > turns out to be 50 LOC more), one doesn't have to be expert at writing
> > JOIN queries or such, but just can run the function, which actually
> > takes way less time (3sec) to scan the same 5mn WAL records [3].
>
> That's exactly my concern, yes. As you say, it's not just the
> performance aspect. Requiring users to write a needlessly ornamental
> query is actively misleading. It suggests that block_ref is distinct
> information from the blocks output by pg_get_wal_block_info().

+1 for pg_get_wal_block_info emitting per-record WAL info too along
with block info, attached v2 patch does that. IMO, usability wins the
race here.

-- 
Bharath Rupireddy
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com

Commits

  1. Add show_data option to pg_get_wal_block_info.

  2. Show record information in pg_get_wal_block_info.

  3. Fix recent pg_walinspect fpi_length bug.

  4. Improve a few things in pg_walinspect

  5. Rework design of functions in pg_walinspect

  6. pg_walinspect: pg_get_wal_fpi_info() -> pg_get_wal_block_info()