Re: wal_compression = on: what is the algorithm?

On Fri, Nov 15, 2024 at 03:30:59PM +0000, PG Doc comments form wrote:
> The following documentation comment has been logged on the website:
>
> Page: https://www.postgresql.org/docs/16/runtime-config-wal.html
> Description:
>
> In
> https://www.postgresql.org/docs/16/runtime-config-wal.html#GUC-WAL-COMPRESSION,
> the option "on" is not described:
>
> “The supported methods are pglz, lz4 (if PostgreSQL was compiled with
> --with-lz4) and zstd (if PostgreSQL was compiled with --with-zstd). The
> default value is off. ”
>
> "on" was an available option before PG 15, and still seen in some docs.
> If I understand the code in src/backend/utils/misc/guc_tables.c, "on" is the
> same as "pglz". So I suggest:
>
> “The supported methods are pglz, lz4 (if PostgreSQL was compiled with
> --with-lz4) and zstd (if PostgreSQL was compiled with --with-zstd). The
> default value is off. The value on is synonym of pglz.”

I think we kept 'on' just for backward compatibility, so we don't
mention it in the docs anymore.

--
Bruce Momjian <bruce(at)momjian(dot)us> https://momjian.us
EDB https://enterprisedb.com

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