On Mar 1, 2010, at 4:35 PM, Tom Lane wrote: > Theo Schlossnagle <je...@omniti.com> writes: >> I'm writing some extension and I have a hot code path that has a lot of >> double (C type) data and needs to output NUMERIC tuple data. The current >> methods I can find in the code to convert sprintf the double to a buffer and >> then invoke the numeric_in function on them. I've profile my stuff and I'm >> spending (wasting) all my time in that conversion. Is there a more >> efficient method of converting a double into a postgres numeric value? > > If you're worried about micro-optimization, why are you using NUMERIC at > all? It's no speed demon. > > Although you might be able to shave some cycles with a dedicated code > path for this conversion, binary to decimal is fundamentally not cheap.
I feared that was the case. I spent an hour or so coding that last night and the speedups for me were worth it, I see a 2 fold speedup in conversion operations (or a 50% reduction in CPU cycles per conversion). The integer ones were trivial, the double one has the imperfect issue of reasonably guessing the dscale, but seems to work in my tests. I didn't look deeply at the postgres internals to see if there was a way to do double -> numeric and integer-types -> numeric without intermediary string format. If that sort of thing is easy to leverage, I'd be happy to share the code. -- Theo Schlossnagle http://omniti.com/is/theo-schlossnagle -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
