Re: [HACKERS] Parallel tuplesort (for parallel B-Tree index creation)

Robert Haas wrote:

> + * To support parallel sort operations involving coordinated callers to
> + * tuplesort.c routines across multiple workers, it is necessary to
> + * concatenate each worker BufFile/tapeset into one single leader-wise
> + * logical tapeset. Workers should have produced one final materialized
> + * tape (their entire output) when this happens in leader; there will always
> + * be the same number of runs as input tapes, and the same number of input
> + * tapes as workers.
>
> I can't interpret the word "leader-wise". A partition-wise join is a
> join done one partition at a time, but a leader-wise logical tape set
> is not done one leader at a time. If there's another meaning to the
> affix -wise, I'm not familiar with it. Don't we just mean "a single
> logical tapeset managed by the leader"?

https://www.merriam-webster.com/dictionary/-wise
-wise
adverb combining form
Definition of -wise
1 a : in the manner of crabwise fanwise
b : in the position or direction of slantwise clockwise
2 : with regard to : in respect of dollarwise

I think "one at a time" is not the right way to interpret the affix.
Rather, a "partitionwise join" is a join done "in the manner of
partitions", that is, the characteristics of the partitions are
considered when the join is done.

I'm not defending the "leader-wise" term here, though, because I can't
make sense of it, regardless of how I interpret the -wise affix.

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Álvaro Herrera https://www.2ndQuadrant.com/
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