Allow incremental sorts for windowing functions

This expands on the work done in d2d8a229b and allows incremental sort
to be considered during create_window_paths().

Author: David Rowley
Reviewed-by: Daniel Gustafsson, Tomas Vondra
Discussion: https://postgr.es/m/CAApHDvoOHobiA2x13NtWnWLcTXYj9ddpCkv9PnAJQBMegYf_xw%40mail.gmail.com

diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index 139c5e3dc245fd51152f7c05de3680d02c3444a8..8007e205ed77c072f5bde9fe821a94e3b7d84fc5 100644 (file)
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -4582,14 +4582,17 @@ create_window_paths(PlannerInfo *root,
    /*
     * Consider computing window functions starting from the existing
     * cheapest-total path (which will likely require a sort) as well as any
-    * existing paths that satisfy root->window_pathkeys (which won't).
+    * existing paths that satisfy or partially satisfy root->window_pathkeys.
     */
    foreach(lc, input_rel->pathlist)
    {
        Path       *path = (Path *) lfirst(lc);
+       int         presorted_keys;
 
        if (path == input_rel->cheapest_total_path ||
-           pathkeys_contained_in(root->window_pathkeys, path->pathkeys))
+           pathkeys_count_contained_in(root->window_pathkeys, path->pathkeys,
+                                       &presorted_keys) ||
+           presorted_keys > 0)
            create_one_window_path(root,
                                   window_rel,
                                   path,
@@ -4664,18 +4667,42 @@ create_one_window_path(PlannerInfo *root,
    {
        WindowClause *wc = lfirst_node(WindowClause, l);
        List       *window_pathkeys;
+       int         presorted_keys;
+       bool        is_sorted;
 
        window_pathkeys = make_pathkeys_for_window(root,
                                                   wc,
                                                   root->processed_tlist);
 
+       is_sorted = pathkeys_count_contained_in(window_pathkeys,
+                                               path->pathkeys,
+                                               &presorted_keys);
+
        /* Sort if necessary */
-       if (!pathkeys_contained_in(window_pathkeys, path->pathkeys))
+       if (!is_sorted)
        {
-           path = (Path *) create_sort_path(root, window_rel,
-                                            path,
-                                            window_pathkeys,
-                                            -1.0);
+           /*
+            * No presorted keys or incremental sort disabled, just perform a
+            * complete sort.
+            */
+           if (presorted_keys == 0 || !enable_incremental_sort)
+               path = (Path *) create_sort_path(root, window_rel,
+                                                path,
+                                                window_pathkeys,
+                                                -1.0);
+           else
+           {
+               /*
+                * Since we have presorted keys and incremental sort is
+                * enabled, just use incremental sort.
+                */
+               path = (Path *) create_incremental_sort_path(root,
+                                                            window_rel,
+                                                            path,
+                                                            window_pathkeys,
+                                                            presorted_keys,
+                                                            -1.0);
+           }
        }
 
        if (lnext(activeWindows, l))

diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 13c91c9916fa929d81e2a75c1b5f0d0b9fa55b1e..21c6cac491f1c4471f0d66d3851c21eab1dc81f7 100644 (file)
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -3200,6 +3200,50 @@ FROM empsalary;
                ->  Seq Scan on empsalary
 (5 rows)
 
+-- Test incremental sorting
+EXPLAIN (COSTS OFF)
+SELECT * FROM
+  (SELECT depname,
+          empno,
+          salary,
+          enroll_date,
+          row_number() OVER (PARTITION BY depname ORDER BY enroll_date) AS first_emp,
+          row_number() OVER (PARTITION BY depname ORDER BY enroll_date DESC) AS last_emp
+   FROM empsalary) emp
+WHERE first_emp = 1 OR last_emp = 1;
+                                    QUERY PLAN                                     
+-----------------------------------------------------------------------------------
+ Subquery Scan on emp
+   Filter: ((emp.first_emp = 1) OR (emp.last_emp = 1))
+   ->  WindowAgg
+         ->  Incremental Sort
+               Sort Key: empsalary.depname, empsalary.enroll_date
+               Presorted Key: empsalary.depname
+               ->  WindowAgg
+                     ->  Sort
+                           Sort Key: empsalary.depname, empsalary.enroll_date DESC
+                           ->  Seq Scan on empsalary
+(10 rows)
+
+SELECT * FROM
+  (SELECT depname,
+          empno,
+          salary,
+          enroll_date,
+          row_number() OVER (PARTITION BY depname ORDER BY enroll_date) AS first_emp,
+          row_number() OVER (PARTITION BY depname ORDER BY enroll_date DESC) AS last_emp
+   FROM empsalary) emp
+WHERE first_emp = 1 OR last_emp = 1;
+  depname  | empno | salary | enroll_date | first_emp | last_emp 
+-----------+-------+--------+-------------+-----------+----------
+ develop   |     8 |   6000 | 10-01-2006  |         1 |        5
+ develop   |     7 |   4200 | 01-01-2008  |         5 |        1
+ personnel |     2 |   3900 | 12-23-2006  |         1 |        2
+ personnel |     5 |   3500 | 12-10-2007  |         2 |        1
+ sales     |     1 |   5000 | 10-01-2006  |         1 |        3
+ sales     |     4 |   4800 | 08-08-2007  |         3 |        1
+(6 rows)
+
 -- cleanup
 DROP TABLE empsalary;
 -- test user-defined window function with named args and default args

diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index af206ca4664e292bb722b71849c796116d30d703..9485aebce85c25fd9bdb54cd36a41429a032dccb 100644 (file)
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -936,6 +936,28 @@ SELECT
   lag(1) OVER (PARTITION BY depname ORDER BY salary,enroll_date,empno)
 FROM empsalary;
 
+-- Test incremental sorting
+EXPLAIN (COSTS OFF)
+SELECT * FROM
+  (SELECT depname,
+          empno,
+          salary,
+          enroll_date,
+          row_number() OVER (PARTITION BY depname ORDER BY enroll_date) AS first_emp,
+          row_number() OVER (PARTITION BY depname ORDER BY enroll_date DESC) AS last_emp
+   FROM empsalary) emp
+WHERE first_emp = 1 OR last_emp = 1;
+
+SELECT * FROM
+  (SELECT depname,
+          empno,
+          salary,
+          enroll_date,
+          row_number() OVER (PARTITION BY depname ORDER BY enroll_date) AS first_emp,
+          row_number() OVER (PARTITION BY depname ORDER BY enroll_date DESC) AS last_emp
+   FROM empsalary) emp
+WHERE first_emp = 1 OR last_emp = 1;
+
 -- cleanup
 DROP TABLE empsalary;