Simon Riggs <[EMAIL PROTECTED]> writes:
> I still do, for multi-user systems. Releasing unused memory from a large
> CREATE INDEX will allow that memory to be swapped out, even if the brk
> point can't be changed.

Say what?  It can get "swapped out" anyway, whether we free() it or not.

More to the point, though: I don't believe that the proposed patch is a
good idea --- it does not reduce the peak sortmem use, which I think is
the critical factor for a multiuser system, and what it does do is
reduce the locality of access to the sort temp file during the merge
phases.  That will definitely have some impact; maybe small, but some;
and I don't see where the benefit comes in.

                        regards, tom lane

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TIP 9: In versions below 8.0, the planner will ignore your desire to
       choose an index scan if your joining column's datatypes do not

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