Improve EXPLAIN's display of window functions.

Up to now we just punted on showing the window definitions used
in a plan, with window function calls represented as "OVER (?)".
To improve that, show the window definition implemented by each
WindowAgg plan node, and reference their window names in OVER.
For nameless window clauses generated by "OVER (...)", assign
unique names w1, w2, etc.

In passing, re-order the properties shown for a WindowAgg node
so that the Run Condition (if any) appears after the Window
property and before the Filter (if any).  This seems more
sensible since the Run Condition is associated with the Window
and acts before the Filter.

Thanks to David G. Johnston and Álvaro Herrera for design
suggestions.

Author: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: David Rowley <dgrowleyml@gmail.com>
Discussion: https://postgr.es/m/144530.1741469955@sss.pgh.pa.us

1 files changed, 13 insertions, 26 deletions

diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 816a2b2a576..75e2b0b9036 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -285,12 +285,9 @@ static Memoize *make_memoize(Plan *lefttree, Oid *hashoperators,
 							 Oid *collations, List *param_exprs,
 							 bool singlerow, bool binary_mode,
 							 uint32 est_entries, Bitmapset *keyparamids);
-static WindowAgg *make_windowagg(List *tlist, Index winref,
+static WindowAgg *make_windowagg(List *tlist, WindowClause *wc,
 								 int partNumCols, AttrNumber *partColIdx, Oid *partOperators, Oid *partCollations,
 								 int ordNumCols, AttrNumber *ordColIdx, Oid *ordOperators, Oid *ordCollations,
-								 int frameOptions, Node *startOffset, Node *endOffset,
-								 Oid startInRangeFunc, Oid endInRangeFunc,
-								 Oid inRangeColl, bool inRangeAsc, bool inRangeNullsFirst,
 								 List *runCondition, List *qual, bool topWindow,
 								 Plan *lefttree);
 static Group *make_group(List *tlist, List *qual, int numGroupCols,
@@ -2683,7 +2680,7 @@ create_windowagg_plan(PlannerInfo *root, WindowAggPath *best_path)
 
 	/* And finally we can make the WindowAgg node */
 	plan = make_windowagg(tlist,
-						  wc->winref,
+						  wc,
 						  partNumCols,
 						  partColIdx,
 						  partOperators,
@@ -2692,14 +2689,6 @@ create_windowagg_plan(PlannerInfo *root, WindowAggPath *best_path)
 						  ordColIdx,
 						  ordOperators,
 						  ordCollations,
-						  wc->frameOptions,
-						  wc->startOffset,
-						  wc->endOffset,
-						  wc->startInRangeFunc,
-						  wc->endInRangeFunc,
-						  wc->inRangeColl,
-						  wc->inRangeAsc,
-						  wc->inRangeNullsFirst,
 						  best_path->runCondition,
 						  best_path->qual,
 						  best_path->topwindow,
@@ -6704,18 +6693,16 @@ make_agg(List *tlist, List *qual,
 }
 
 static WindowAgg *
-make_windowagg(List *tlist, Index winref,
+make_windowagg(List *tlist, WindowClause *wc,
 			   int partNumCols, AttrNumber *partColIdx, Oid *partOperators, Oid *partCollations,
 			   int ordNumCols, AttrNumber *ordColIdx, Oid *ordOperators, Oid *ordCollations,
-			   int frameOptions, Node *startOffset, Node *endOffset,
-			   Oid startInRangeFunc, Oid endInRangeFunc,
-			   Oid inRangeColl, bool inRangeAsc, bool inRangeNullsFirst,
 			   List *runCondition, List *qual, bool topWindow, Plan *lefttree)
 {
 	WindowAgg  *node = makeNode(WindowAgg);
 	Plan	   *plan = &node->plan;
 
-	node->winref = winref;
+	node->winname = wc->name;
+	node->winref = wc->winref;
 	node->partNumCols = partNumCols;
 	node->partColIdx = partColIdx;
 	node->partOperators = partOperators;
@@ -6724,17 +6711,17 @@ make_windowagg(List *tlist, Index winref,
 	node->ordColIdx = ordColIdx;
 	node->ordOperators = ordOperators;
 	node->ordCollations = ordCollations;
-	node->frameOptions = frameOptions;
-	node->startOffset = startOffset;
-	node->endOffset = endOffset;
+	node->frameOptions = wc->frameOptions;
+	node->startOffset = wc->startOffset;
+	node->endOffset = wc->endOffset;
 	node->runCondition = runCondition;
 	/* a duplicate of the above for EXPLAIN */
 	node->runConditionOrig = runCondition;
-	node->startInRangeFunc = startInRangeFunc;
-	node->endInRangeFunc = endInRangeFunc;
-	node->inRangeColl = inRangeColl;
-	node->inRangeAsc = inRangeAsc;
-	node->inRangeNullsFirst = inRangeNullsFirst;
+	node->startInRangeFunc = wc->startInRangeFunc;
+	node->endInRangeFunc = wc->endInRangeFunc;
+	node->inRangeColl = wc->inRangeColl;
+	node->inRangeAsc = wc->inRangeAsc;
+	node->inRangeNullsFirst = wc->inRangeNullsFirst;
 	node->topWindow = topWindow;
 
 	plan->targetlist = tlist;