Read from the same worker repeatedly until it returns no tuple. The original coding read tuples from workers in round-robin fashion, but performance testing shows that it works much better to read enough to empty one queue before moving on to the next. I believe the reason for this is that, with the old approach, we could easily wake up a worker repeatedly to write only one new tuple into the shm_mq each time. With this approach, by the time the process gets scheduled, it has a decent chance of being able to fill the entire buffer in one go.
Patch by me. Dilip Kumar helped with performance testing. Branch ------ master Details ------- http://git.postgresql.org/pg/commitdiff/bc7fcab5e36b9597857fa7e3fa6d9ba54aaea167 Modified Files -------------- src/backend/executor/nodeGather.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) -- Sent via pgsql-committers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-committers
