Tomas Vondra <tomas.vondra@enterprisedb.com> writes:
> On 12/22/20 8:03 PM, Tom Lane wrote:
>> The link Ken pointed at suggests that restricting the window size to
>> 8MB is a common compromise. It's not clear to me what that does to
>> the achievable compression ratio. Even 8MB could be an annoying cost
>> if it's being paid per-process, on both the server and client sides.
> Possibly, but my understanding is that's merely a recommendation for the
> decoder library (e.g. libzstd), and it's not clear to me if/how that
> relates to the compression level or how to influence it.
> From the results shared by Daniil, the per-client overhead seems way
> higher than 8MB, so either libzstd does not respect this recommendation
> or maybe there's something else going on.
I'd assume that there's a direct correlation between the compression level
setting and the window size; but I've not studied the libzstd docs in
enough detail to know what it is.
regards, tom lane