On Fri, Sep 22, 2017 at 11:09 PM, Robert Haas <robertmh...@gmail.com> wrote: > During planning, *every* node has a list of pathkeys associated with > it which represent the presumed output ordering. You can support > ordered append paths without changing any data structures at all; it's > just a matter of putting pathkeys into an AppendPath. >
I totally agree. > The reason why MergeAppend has extra stuff in the node (numCols, > sortColIdx, etc.) is so that it can actually perform the sort at > runtime. But this feature requires no runtime support -- that's kinda > the point -- so there's no need for it to carry that information, or > to add any new nodes. > > At least, IIUC. That's true, but numCols, sortColdIdx etc are also used to display the sort key in an explain. If an append can return sorted data, it should also display the sort information, so I think these fields are still required in an Append node. If it's ok to only add these fields in an Append node for the explain part, I'll revert the Append/MergeAppend refactoring and do some other cleanup as you advised earlier. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
