A couple questions about ordered-set aggregates

On Sun, Oct 25, 2020 at 09:32:22PM -0400, Chapman Flack wrote:

I find I am allowed to create an ordered-set aggregate with a non-empty
direct argument list and no finisher function. Am I right in thinking
that's kind of nonsensical, as nothing will ever look at the direct args?

Also, the syntax summary shows PARALLEL = { SAFE | RESTRICTED | UNSAFE }
in the ordered-set syntax variant, since 9.6, though that variant
accepts no combine/serial/deserial functions, and there's also
a note saying "Partial (including parallel) aggregation is currently
not supported for ordered-set aggregates."

Does PARALLEL = { SAFE | RESTRICTED | UNSAFE } on an ordered-set
aggregate affect anything?

I may be missing something, but I believe PARALLEL = SAFE simply means
it can be executed in the parallel part of the plan. That does not
require support for partial aggregation - we simply don't support
passing partial results to the leader, hence combine/serial/deserial
functions are not needed.

Not sure about the direct arguments.

regards

--
Tomas Vondra http://www.2ndQuadrant.com
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