On Sun, Dec 5, 2010 at 6:01 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Itagaki Takahiro <itagaki.takah...@gmail.com> writes: >> On Fri, Dec 3, 2010 at 18:02, Dimitri Fontaine <dimi...@2ndquadrant.fr> >> wrote: >>> My understanding is that the variadic form shadows the other one in a >>> way that it's now impossible to call it from SQL level. That's the >>> reason why I did the (text, text, text, VARIADIC text) version before, >>> but is it true? > >> The VARIADIC version doesn't hide the 3-args version. I tested the >> behavior by printf-debug. The planner seems to think the non VARIADIC >> version is the best-matched one when 3 arguments are passed. > > Why is there a variadic replace() in this patch at all? It seems just > about entirely unrelated to the stated purpose of the patch, as well > as being of dubious usefulness. When would it be superior to > > replace(replace(orig, from1, to1), from2, to2), ... > > The implementation doesn't appear to offer any material speed > improvement over nested calls of that sort, and I'm finding it hard to > visualize when it would be more useful than nested calls. The > documentation is entirely inadequate as well.
An iterated replacement has different semantics from a simultaneous replace - replacing N placeholders with values simultaneously means you don't need to worry about the case where one of the replacement strings contains something that looks like a placeholder. I actually think a simultaneous replacement feature would be quite handy but I make no comment on whether it belongs as part of this patch. The discussion on this patch has been rather wide-ranging, and it's not clear to me that there's really consensus on what this patch needs to - or should - do. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
