On 12/17/2017 04:32 AM, Robert Haas wrote: > On Thu, Dec 14, 2017 at 12:23 PM, Tomas Vondra > <tomas.von...@2ndquadrant.com> wrote: >> Can you give an example of such algorithm? Because I haven't seen such >> example, and I find arguments based on hypothetical compression methods >> somewhat suspicious. >> >> FWIW I'm not against considering such compression methods, but OTOH it >> may not be such a great primary use case to drive the overall design. > > Well it isn't, really. I am honestly not sure what we're arguing > about at this point. I think you've agreed that (1) opening avenues > for extensibility is useful, (2) substitution a general-purpose > compression algorithm could be useful, and (3) having datatype > compression that is enabled through TOAST rather than built into the > datatype might sometimes be desirable. That's more than adequate > justification for this proposal, whether half-general compression > methods exist or not. I am prepared to concede that there may be no > useful examples of such a thing. >
I don't think we're arguing - we're discussing if a proposed patch is the right design solving relevant use cases. I personally am not quite convinced about that, for the reason I tried to explain in my previous messages. I see it as a poor alternative to compression built into the data type. I do like the idea of compression with external dictionary, however. But don't forget that it's not me in this thread - it's my evil twin, moonlighting as Mr. Devil's lawyer ;-) -- Tomas Vondra http://www.2ndQuadrant.com PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services