On Thu, Sep 22, 2016 at 3:51 PM, Heikki Linnakangas <hlinn...@iki.fi> wrote:
> It'd be good if you could overlap the final merges in the workers with the
> merge in the leader. ISTM it would be quite straightforward to replace the
> final tape of each worker with a shared memory queue, so that the leader
> could start merging and returning tuples as soon as it gets the first tuple
> from each worker. Instead of having to wait for all the workers to complete
> first.

If you do that, make sure to have the leader read multiple tuples at a
time from each worker whenever possible.  It makes a huge difference
to performance.  See bc7fcab5e36b9597857fa7e3fa6d9ba54aaea167.

Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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