Horton

Re: ZStandard (with dictionaries) compression support for TOAST compression

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Nikhil Kumar Veldanda <veldanda.nikhilkumar17@gmail.com>
Cc: Michael Paquier <michael@paquier.xyz>, pgsql-hackers@postgresql.org
Date: 2025-05-05T15:07:01Z
Lists: pgsql-hackers

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  1. Split regression tests for TOAST compression methods into two files

  2. Refactor non-supported compression error message in toast_compression.c

On Sun, May 4, 2025 at 8:54 AM Nikhil Kumar Veldanda
<veldanda.nikhilkumar17@gmail.com> wrote:
> I agree. Each compression algorithm can decide its own metadata size
> overhead. Callbacks can provide this information as well rather than
> storing in fixed length bytes(3 bytes). The revised patch introduces a
> "toast_cmpid_meta_size(const varatt_cmp_extended *hdr)", which
> calculates the metadata size.

I don't understand why we need this. I don't see why we need any sort
of generalized concept of metadata at all here. The zstd-dict
compression method needs to store a four-byte OID, so let it do that.
But we don't need to brand that as metadata; and we don't need a
method for other parts of the system to ask how much metadata exists.
At least, I don't think we do.

-- 
Robert Haas
EDB: http://www.enterprisedb.com