Hi all! I decided to start new thread for this patch for following two reasons. * It's renamed from "Partial sort" to "Incremental sort" per suggestion by Robert Haas . New name much better characterizes the essence of algorithm. * I think it's not PoC anymore. Patch received several rounds of review and now it's in the pretty good shape.
Attached revision of patch has following changes. * According to review , two new path and plan nodes are responsible for incremental sort: IncSortPath and IncSort which are inherited from SortPath and Sort correspondingly. That allowed to get rid of set of hacks with minimal code changes. * According to review  and comment , previous tuple is stored in standalone tuple slot of SortState rather than just HeapTuple. * New GUC parameter enable_incsort is introduced to control planner ability to choose incremental sort. * Test of postgres_fdw with not pushed down cross join is corrected. It appeared that with incremental sort such query is profitable to push down. I changed ORDER BY columns so that index couldn't be used. I think this solution is more elegant than setting enable_incsort = off. Also patch has set of assorted code and comments improvements. Links 1. https://www.postgresql.org/message-id/CA+TgmoZapyHRm7NVyuyZ+yAV=u1a070bogre7pkgyraegr4...@mail.gmail.com 2. https://www.postgresql.org/message-id/cam3swzql4yd2sndhemcgl0q2b2otdkuvv_l6zg_fcgoluwm...@mail.gmail.com ------ Alexander Korotkov Postgres Professional: http://www.postgrespro.com The Russian Postgres Company
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