2010/1/28 Robert Haas <robertmh...@gmail.com>: > On Thu, Jan 28, 2010 at 10:56 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: >> Robert Haas <robertmh...@gmail.com> writes: >>> On Thu, Jan 28, 2010 at 9:01 AM, Pavel Stehule <pavel.steh...@gmail.com> >>> wrote: >>>> simplest could not be a best. There have to be only a const >>>> expression. But we have not possibility to check it in pg. >> >>> Well... that's an entirely arbitrary limitation. I admit that it >>> doesn't seem likely that someone would want to have a variable >>> delimiter, but putting extra effort and code complexity into >>> preventing it seems pointless. >> >> Yeah. The real issue here is that in some cases you'd like to have >> non-aggregated parameters to an aggregate, but SQL has no notation >> to express that. > > Right. > >> I think Pavel's underlying complaint is that if the delimiter >> argument isn't constant, then we're exposing an implementation >> dependency in terms of just which values get separated by which >> delimiters. The most practical implementation seems to be that >> the first-call delimiter isn't actually used at all, and on >> subsequent calls the delimiter *precedes* the associated value, >> which is a bit surprising given the order in which one writes >> them. Not sure if this is worth documenting though. Those two >> or three people who actually try it will figure it out soon enough. >
ok - there is one query, in 99.99% the second argument will be a constant. Can we use this information and optimize function for this case? The detoast on every row can take some percent from a performance. Pavel > Yeah, I'm thoroughly unworried about it. > > ...Robert > -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
