On 2 November 2017 at 01:55, Robert Haas <robertmhaas@gmail.com> wrote:
> On Wed, Nov 1, 2017 at 7:49 AM, Craig Ringer <craig@2ndquadrant.com> wrote:
>> If the client wants to fetch in chunks it can use a portal and limited
>> size fetches. That shouldn't (?) be parallel-unsafe, since nothing
>> else can happen in the middle anyway.
>
> I believe sending a limited-size fetch forces serial execution
> currently. If it's true that nothing else can happen in the middle
> then we could relax that, but I don't see why that should be true?
Perhaps the question is not "why" but "when"?
If a parallel cursor is requested, we could simply prevent other
intermediate commands other than FETCH (next).
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
