On Thu, Sep 29, 2016 at 6:52 AM, Peter Geoghegan <p...@heroku.com> wrote: >> How is it awkward? > > Maybe that was the wrong choice of words. What I mean is that it seems > somewhat unprincipled to give over an equal share of memory to each > active-at-least-once tape, ...
I don't get it. If the memory is being used for prereading, then the point is just to avoid doing many small I/Os instead of one big I/O, and that goal will be accomplished whether the memory is equally distributed or not; indeed, it's likely to be accomplished BETTER if the memory is equally distributed than if it isn't. I can imagine that there might be a situation in which it makes sense to give a bigger tape more resources than a smaller one; for example, if one were going to divide N tapes across K worker processess and make individual workers or groups of workers responsible for sorting particular tapes, one would of course want to divide up the data across the available processes relatively evenly, rather than having some workers responsible for only a small amount of data and others for a very large amount of data. But such considerations are irrelevant here. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
