* Tom Lane ([EMAIL PROTECTED]) wrote: > "Luke Lonergan" <[EMAIL PROTECTED]> writes: > > I would only suggest that we replace the existing algorithm with one that > > will work regardless of (reasonable) memory requirements. Perhaps we can > > agree that at least 1MB of RAM for external sorting will always be available > > and proceed from there? > > If you can sort indefinitely large amounts of data with 1MB work_mem, > go for it.
It seems you two are talking past each other and I'm at least slightly
confused. So, I'd like to ask for a bit of clarification and perhaps
that will help everyone.
#1: I'm as much a fan of eliminating unnecessary code as anyone
#2: There have been claims of two-pass improving things 400%
#3: Supposedly two-pass requires on the order of sqrt(total) memory
#4: We have planner statistics to estimate size of total
#5: We have a work_mem limitation for a reason
So, if we get a huge performance increase, what's wrong with:
if [ sqrt(est(total)) <= work_mem ]; then
two-pass-sort();
else
tape-sort();
fi
?
If the performance isn't much different and tape-sort can do it with
less memory then I don't really see any point in removing it.
If the intent is to remove it and then ask for the default work_mem to
be increased- I doubt going about it this way would work very well. :)
Thanks,
Stephen
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