|From:||Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>|
|Subject:||[PATCH] Incremental sort (was: PoC: Partial sort)|
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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
* 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.
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