Teach planner about more monotonic window functions

9d9c02ccd introduced runConditions for window functions to allow
monotonic window function evaluation to be made more efficient when the
window function value went beyond some value that it would never go back
from due to its monotonic nature.  That commit added prosupport functions
to inform the planner that row_number(), rank(), dense_rank() and some
forms of count(*) were monotonic.  Here we add support for ntile(),
cume_dist() and percent_rank().

Reviewed-by: Melanie Plageman
Discussion: https://postgr.es/m/CAApHDvqR+VqB8s+xR-24bzJbU8xyFrBszJ17qKgECf7cWxLCaA@mail.gmail.com

diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index af13b8e53d5c45c052030fc8be7183ea0a9e15aa..b87a624fb2fc56762d66f4b9889de22fb97a3444 100644 (file)
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -288,6 +288,15 @@ window_percent_rank_support(PG_FUNCTION_ARGS)
 {
    Node       *rawreq = (Node *) PG_GETARG_POINTER(0);
 
+   if (IsA(rawreq, SupportRequestWFuncMonotonic))
+   {
+       SupportRequestWFuncMonotonic *req = (SupportRequestWFuncMonotonic *) rawreq;
+
+       /* percent_rank() is monotonically increasing */
+       req->monotonic = MONOTONICFUNC_INCREASING;
+       PG_RETURN_POINTER(req);
+   }
+
    if (IsA(rawreq, SupportRequestOptimizeWindowClause))
    {
        SupportRequestOptimizeWindowClause *req = (SupportRequestOptimizeWindowClause *) rawreq;
@@ -362,6 +371,15 @@ window_cume_dist_support(PG_FUNCTION_ARGS)
 {
    Node       *rawreq = (Node *) PG_GETARG_POINTER(0);
 
+   if (IsA(rawreq, SupportRequestWFuncMonotonic))
+   {
+       SupportRequestWFuncMonotonic *req = (SupportRequestWFuncMonotonic *) rawreq;
+
+       /* cume_dist() is monotonically increasing */
+       req->monotonic = MONOTONICFUNC_INCREASING;
+       PG_RETURN_POINTER(req);
+   }
+
    if (IsA(rawreq, SupportRequestOptimizeWindowClause))
    {
        SupportRequestOptimizeWindowClause *req = (SupportRequestOptimizeWindowClause *) rawreq;
@@ -465,6 +483,18 @@ window_ntile_support(PG_FUNCTION_ARGS)
 {
    Node       *rawreq = (Node *) PG_GETARG_POINTER(0);
 
+   if (IsA(rawreq, SupportRequestWFuncMonotonic))
+   {
+       SupportRequestWFuncMonotonic *req = (SupportRequestWFuncMonotonic *) rawreq;
+
+       /*
+        * ntile() is monotonically increasing as the number of buckets cannot
+        * change after the first call
+        */
+       req->monotonic = MONOTONICFUNC_INCREASING;
+       PG_RETURN_POINTER(req);
+   }
+
    if (IsA(rawreq, SupportRequestOptimizeWindowClause))
    {
        SupportRequestOptimizeWindowClause *req = (SupportRequestOptimizeWindowClause *) rawreq;

diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 26e2df6da55581e98bce50b2d9f3f21bf374203e..747608e3c145230d8f72bab1b763b897c2ff8ee3 100644 (file)
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -3766,19 +3766,20 @@ SELECT * FROM
           count(salary) OVER (PARTITION BY depname || '') c1, -- w1
           row_number() OVER (PARTITION BY depname) rn, -- w2
           count(*) OVER (PARTITION BY depname) c2, -- w2
-          count(*) OVER (PARTITION BY '' || depname) c3 -- w3
+          count(*) OVER (PARTITION BY '' || depname) c3, -- w3
+          ntile(2) OVER (PARTITION BY depname) nt -- w2
    FROM empsalary
-) e WHERE rn <= 1 AND c1 <= 3;
-                                        QUERY PLAN                                         
--------------------------------------------------------------------------------------------
+) e WHERE rn <= 1 AND c1 <= 3 AND nt < 2;
+                                          QUERY PLAN                                           
+-----------------------------------------------------------------------------------------------
  Subquery Scan on e
    ->  WindowAgg
-         Filter: ((row_number() OVER (?)) <= 1)
+         Filter: (((row_number() OVER (?)) <= 1) AND ((ntile(2) OVER (?)) < 2))
          Run Condition: (count(empsalary.salary) OVER (?) <= 3)
          ->  Sort
                Sort Key: (((empsalary.depname)::text || ''::text))
                ->  WindowAgg
-                     Run Condition: (row_number() OVER (?) <= 1)
+                     Run Condition: ((row_number() OVER (?) <= 1) AND (ntile(2) OVER (?) < 2))
                      ->  Sort
                            Sort Key: empsalary.depname
                            ->  WindowAgg
@@ -3793,13 +3794,14 @@ SELECT * FROM
           count(salary) OVER (PARTITION BY depname || '') c1, -- w1
           row_number() OVER (PARTITION BY depname) rn, -- w2
           count(*) OVER (PARTITION BY depname) c2, -- w2
-          count(*) OVER (PARTITION BY '' || depname) c3 -- w3
+          count(*) OVER (PARTITION BY '' || depname) c3, -- w3
+          ntile(2) OVER (PARTITION BY depname) nt -- w2
    FROM empsalary
-) e WHERE rn <= 1 AND c1 <= 3;
-  depname  | empno | salary | enroll_date | c1 | rn | c2 | c3 
------------+-------+--------+-------------+----+----+----+----
- personnel |     5 |   3500 | 12-10-2007  |  2 |  1 |  2 |  2
- sales     |     3 |   4800 | 08-01-2007  |  3 |  1 |  3 |  3
+) e WHERE rn <= 1 AND c1 <= 3 AND nt < 2;
+  depname  | empno | salary | enroll_date | c1 | rn | c2 | c3 | nt 
+-----------+-------+--------+-------------+----+----+----+----+----
+ personnel |     5 |   3500 | 12-10-2007  |  2 |  1 |  2 |  2 |  1
+ sales     |     3 |   4800 | 08-01-2007  |  3 |  1 |  3 |  3 |  1
 (2 rows)
 
 -- Tests to ensure we don't push down the run condition when it's not valid to

diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index b7bd0a83da4c6731694aedbf9949fb407ee847b3..1009b438def9e4ea0e13e671116f2da0a17afe95 100644 (file)
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -1220,9 +1220,10 @@ SELECT * FROM
           count(salary) OVER (PARTITION BY depname || '') c1, -- w1
           row_number() OVER (PARTITION BY depname) rn, -- w2
           count(*) OVER (PARTITION BY depname) c2, -- w2
-          count(*) OVER (PARTITION BY '' || depname) c3 -- w3
+          count(*) OVER (PARTITION BY '' || depname) c3, -- w3
+          ntile(2) OVER (PARTITION BY depname) nt -- w2
    FROM empsalary
-) e WHERE rn <= 1 AND c1 <= 3;
+) e WHERE rn <= 1 AND c1 <= 3 AND nt < 2;
 
 -- Ensure we correctly filter out all of the run conditions from each window
 SELECT * FROM
@@ -1230,9 +1231,10 @@ SELECT * FROM
           count(salary) OVER (PARTITION BY depname || '') c1, -- w1
           row_number() OVER (PARTITION BY depname) rn, -- w2
           count(*) OVER (PARTITION BY depname) c2, -- w2
-          count(*) OVER (PARTITION BY '' || depname) c3 -- w3
+          count(*) OVER (PARTITION BY '' || depname) c3, -- w3
+          ntile(2) OVER (PARTITION BY depname) nt -- w2
    FROM empsalary
-) e WHERE rn <= 1 AND c1 <= 3;
+) e WHERE rn <= 1 AND c1 <= 3 AND nt < 2;
 
 -- Tests to ensure we don't push down the run condition when it's not valid to
 -- do so.