Re: Merge algorithms for large numbers of "tapes"

Yes ­ all of the current best practice external sorts use two passes. A
first to produce the runs, which results in ³S² number of ³files², then a
single merge pass across the runs. At most 1 pass across the S runs is
required to implement the merge.

- Luke

On 3/7/06 8:03 PM, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> "Luke Lonergan" <llonergan(at)greenplum(dot)com> writes:
>> > Two passes is the state-of-the-practice on external disk sorts.
>
> There is no such thing as a fixed number of passes regardless of
> available memory and size of the data.
>
> regards, tom lane
>
>