On Thu, Sep 11, 2014 at 07:17:42PM +0200, Andres Freund wrote: > On 2014-09-11 13:04:43 -0400, Robert Haas wrote: > > On Thu, Sep 11, 2014 at 12:58 PM, Andres Freund <and...@2ndquadrant.com> > > wrote: > > > On 2014-09-11 12:55:21 -0400, Robert Haas wrote: > > >> I advise supporting pglz only for the initial patch, and adding > > >> support for the others later if it seems worthwhile. The approach > > >> seems to work well enough with pglz that it's worth doing even if we > > >> never add the other algorithms. > > > > > > That approach is fine with me. Note though that I am pretty strongly > > > against adding support for more than one algorithm at the same time. > > > > What if one algorithm compresses better and the other algorithm uses > > less CPU time? > > Then we make a choice for our users. A configuration option about an > aspect of postgres that darned view people will understand with for the > marginal differences between snappy and lz4 doesn't make sense. > > > I don't see a compelling need for an option if we get a new algorithm > > that strictly dominates what we've already got in all parameters, and > > it may well be that, as respects pglz, that's achievable. But ISTM > > that it need not be true in general. > > If you look at the results lz4 is pretty much there. Sure, there's > algorithms which have a much better compression - but the time overhead > is so large it just doesn't make sense for full page compression. > > Greetings, > > Andres Freund >
In addition, you can leverage the the presence of a higher-compression version of lz4 (lz4hc) that can utilize the same decompression engine that could possibly be applied to static tables as a REINDEX option or even slowly growing tables that would benefit from the better compression as well as the increased decompression speed available. Regards, Ken -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
