On Fri, 2007-04-13 at 11:47 -0400, Tom Lane wrote: > "Simon Riggs" <[EMAIL PROTECTED]> writes: > > On Fri, 2007-04-13 at 10:36 -0400, Tom Lane wrote: > >> That's what bothers me about this patch, too. It will be increasing > >> the cost of writing WAL (more data -> more CRC computation and more > >> I/O, not to mention more contention for the WAL locks) which translates > >> directly to a server slowdown. > > > I don't really understand this concern. > > The real objection is that a patch that's alleged to make WAL smaller > actually does the exact opposite. Now maybe you can buy that back > downstream of the archiver --- after yet more added-on processing --- > but it still seems that there's a fundamental misdesign here. > > > Koichi-san has included a parameter setting that would prevent any > > change at all in the way WAL is written. > > It bothers me that we'd need to have such a switch. That's just another > way to shoot yourself in the foot, either by not enabling it (in which > case applying pg_compresslog as it stands would actively break your > WAL), or by enabling it when you weren't actually going to use > pg_compresslog (because you misunderstood the documentation to imply > that it'd make your WAL smaller by itself). What I want to see is a > patch that doesn't bloat WAL at all and therefore doesn't need a switch. > I think Andreas is correct to complain that it should be done that way.
I agree with everything you say because we already had *exactly* this discussion when the patch was already submitted, with me saying everything you just said. After a few things have been renamed to show their correct function and impact, I am now comfortable with this patch. Writing lots of additional code simply to remove a parameter that *might* be mis-interpreted doesn't sound useful to me, especially when bugs may leak in that way. My take is that this is simple and useful *and* we have it now; other ways don't yet exist, nor will they in time for 8.3. -- Simon Riggs EnterpriseDB http://www.enterprisedb.com ---------------------------(end of broadcast)--------------------------- TIP 7: You can help support the PostgreSQL project by donating at http://www.postgresql.org/about/donate