Robert Haas <robertmh...@gmail.com> writes: > On Mon, Dec 11, 2017 at 11:59 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: >> Tomas Vondra <tomas.von...@2ndquadrant.com> writes: >>> On 12/11/2017 05:27 PM, Tom Lane wrote: >>>> However, unless we want to run around and touch all the ~ 150 calls >>>> with constant arguments, we'd have to set things up so that the default >>>> behavior for AllocSetContextCreate is to not copy. This risks breaking >>>> callers in extensions. Not entirely sure if it's worth that --- any >>>> thoughts? >> >>> I don't think silently breaking extensions is particularly attractive >>> option, so I guess we'll have to run around and tweak the ~150 calls. >> >> Meh. I suppose that of the ~150 call sites, there are probably only >> a dozen or two where it would actually make a performance difference, >> so maybe this needn't be quite as invasive as I first thought. > > I think changing only a subset of the call sites is unappealing > because, even though it may not make a measurable performance > difference in other cases, it may get cargo-culted into some place > where it does make a difference.
Would it be acceptable to only get this optimisation on compilers that support __builtin_constant_p or similar? If so, the wrapper macro could use that to automatically pass the no-copy flag when called with a literal string. - ilmari -- "I use RMS as a guide in the same way that a boat captain would use a lighthouse. It's good to know where it is, but you generally don't want to find yourself in the same spot." - Tollef Fog Heen