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 [1].  New name much better characterizes the essence of
 * 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 [1], 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 [1] and comment [2], 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.


Alexander Korotkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company

Attachment: incremental-sort-1.patch
Description: Binary data

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