On 18 March 2016 at 10:13, James Sewell <james.sew...@lisasoft.com> wrote:
> This does bring up an interesting point I don't quite understand though. If I
> run parallel agg on a table with 4 rows with 2 workers will it run on two
> workers (2 rows each) or will the first one grab all 4 rows?
It works on a per page basis, workers just each grab the next page to
be scanned from a page counter that sits in shared memory, the worker
just increments the page number, releases the lock on the counter and
scans that page.
So the answer to your question is probably no. At least not unless the
the page only contained 2 rows.
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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