Re: [HACKERS] Inefficiencies in COPY command

> Tom Lane wrote -
> > Wayne Piekarski <wayne@senet.com.au> writes:
> > > So I made some changes to CopyAttributeOut so that it escapes the string
> > > initially into a temporary buffer (allocated onto the stack) and then
> > > feeds the whole string to the CopySendData which is a lot more efficient
> > > because it can blast the whole string in one go, saving about 1/3 to 1/4
> > > the number of memcpy and so on.
> > 
> > copy.c is pretty much of a hack job to start with, IMHO.  If you can
> > speed it up without making it even uglier, have at it!  However, it
> > also has to be portable, and what you've done here:
> 
> Ok, well I will write up a proper patch for CopyAttributeOut so it is not
> such a hack (using all those #defines and stuff wasn't very "elegant") and
> then submit a proper patch for it.... This was pretty straight forward to
> fix up.

Great.

> 
> > While formatting an int is pretty simple, formatting a float is not so
> > simple.  I'd be leery of replacing sprintf with quick-hack float
> > conversion code.  OTOH, if someone wanted to go to the trouble of doing
> > it *right*, using our own code would tend to yield more consistent
> > results across different OSes, which would be a Good Thing.  I'm not
> > sure it'd be any faster than the typical sprintf, but it might be worth
> > doing anyway.
> 
> I understand there are issues to do with not being able to use GPL code
> with Postgres, because its BSD license is not compatible, but would it be
> acceptable to extract code from BSD style code? If so, my FreeBSD here has
> libc code and includes the internals used by sprintf for rendering
> integers (and floats) and so we could include that code in, and should
> hopefully be portable at the same time as well. 
> 
> This would be a lot faster than going via sprintf and lots of other
> functions, and would make not just COPY, but I think any SELECT query runs
> faster as well (because they get rewritten to strings by the output
> functions don't they). I guess other advantages would be improvements in
> the regression tests maybe, for problem types like int8 which in the past
> have had trouble under some BSDs.

Does using the FreeBSD sprintf conversion functions really make it
faster than just calling sprintf?  How?


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