I thought it makes sense to extend wal_compression to support compression levels.
The patch replaces the simple enum-based setting with string-based 'method[:level]' syntax, similar to the --compress option in pg_dump. What's inside: - Unified GUC design: wal_compression = 'method[:level]' - Supported formats: 'off', 'on', 'pglz', 'lz4[:level]', 'zstd[:level]' - Algorithm-specific defaults: LZ4 defaults to level 1, ZSTD to level 3 when no level is specified. - Parameter validation is performed at SET time. - The string is parsed only once during GUC assignment. - Backward compatibility for common settings: While the GUC type changes from enum to string, common previous boolean-like string values (e.g., 'off', 'true', '0') are handled, mapping to 'pglz' or 'off' correspondingly. - Includes docs change proposal, as well extensive new regression and TAP tests. Additionally, it adds LZ4HC support -- for LZ4, if levels 10-12 are specified, then, when available (checked at build time + runtime), it's supposed to use LZ4HC for higher compression ratio. This part needs additional testing. Originally, I considered adding wal_compression_level but eventually decided to exten wal_compression, because of two reasons: 1. with a separate param, a question of defaults needs to be solved, and I didn't find an elegant solution; 2. "method:level" syntax is already used in another place – pg_dump An early version of this patch was reviewed by Andrey Borodin off-list, and it was extremely helpful. looking forward to seeing feedback Nik
001_wal_compression_with_levels_and_lz4hc.patch
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