Re: Polyphase Merge

Sam Mason <sam@samason.me.uk> writes:
> It's really up to you to find answers to these questions, especially
> the first one.  Once you've designed an efficient algorithm then the
> second point (which I'm interpreting as how you'd go about changing
> tuplestore(?) so that things can be read in reverse order) should
> just drop out as an implementation detail :) I'm guessing you'll
> end up not reading the store in reverse order but arranging things
> differently---it'll be interesting to see.

I agree --- having to read the run back from external storage, only to
write it out again with no further useful work done on it, sounds like
a guaranteed loser.  To make this work you'll need some kind of ju-jitsu
rearrangement that logically puts the run where it needs to go without
physically moving any data.
        regards, tom lane