Horton

Re: [HACKERS] Custom compression methods

Tomas Vondra <tomas.vondra@2ndquadrant.com>

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From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
To: Ildus Kurbangaliev <i.kurbangaliev@postgrespro.ru>
Cc: pgsql-hackers@postgresql.org, Ildar Musin <i.musin@postgrespro.ru>
Date: 2017-11-27T17:20:12Z
Lists: pgsql-hackers 
Hi,

On 11/27/2017 04:52 PM, Ildus Kurbangaliev wrote:
> ...
>
> Hi. This looks like a serious bug, but I couldn't reproduce it yet.
> Did you upgrade some old database or this bug happened after 
> insertion of all data to new database? I tried using your 'archie' 
> tool to download mailing lists and insert them to database, but
> couldn't catch any errors.
> 

I can trigger it pretty reliably with these steps:

    git checkout f65d21b258085bdc8ef2cc282ab1ff12da9c595c
    patch -p1 < ~/custom_compression_methods_v6.patch
    ./configure --enable-debug --enable-cassert \
     CFLAGS="-fno-omit-frame-pointer -O0 -DRANDOMIZE_ALLOCATED_MEMORY" \
     --prefix=/home/postgres/pg-compress
    make -s clean && make -s -j4 install
    cd contrib/
    make -s clean && make -s -j4 install

    export PATH=/home/postgres/pg-compress/bin:$PATH
    pg_ctl -D /mnt/raid/pg-compress init
    pg_ctl -D /mnt/raid/pg-compress -l compress.log start
    createdb archie
    cd ~/archie/sql/
    psql archie < create.sql

    ~/archie/bin/load.py --workers 4 --db archie */* > load.log 2>&1


I guess the trick might be -DRANDOMIZE_ALLOCATED_MEMORY (I first tried
without it, and it seemed working fine). If that's the case, I bet there
is a palloc that should have been palloc0, or something like that.

If you still can't reproduce that, I may give you access to this machine
so that you can debug it there.

regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Commits

  1. docs: Update TOAST storage docs for configurable compression.

  2. Further tweaking of pg_dump's handling of default_toast_compression.

  3. Fix interaction of TOAST compression with expression indexes.

  4. Tidy up more loose ends related to configurable TOAST compression.

  5. Short-circuit slice requests that are for more than the object's size.

  6. Mostly-cosmetic adjustments of TOAST-related macros.

  7. Remove useless configure probe for <lz4/lz4.h>.

  8. Error on invalid TOAST compression in CREATE or ALTER TABLE.

  9. docs: Fix omissions related to configurable TOAST compression.

  10. More code cleanup for configurable TOAST compression.

  11. Bring configure support for LZ4 up to snuff.

  12. Make compression.sql regression test independent of default.

  13. Use valid compression method in brin_form_tuple

  14. Fix up pg_dump's handling of per-attribute compression options.

  15. Allow configurable LZ4 TOAST compression.

  16. Fix inconsistencies in the code

  17. Mostly-cosmetic improvements in memory chunk header alignment coding.

  18. Allow numeric to use a more compact, 2-byte header in many cases.