[CF 5640] v3 - Printing window function OVER clauses in EXPLAIN

This branch was automatically generated by a robot using patches from an
email thread registered at:

https://commitfest.postgresql.org/patch/5640

The branch will be overwritten each time a new patch version is posted to
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on the master branch.

Patch(es): https://www.postgresql.org/message-id/865427.1741623509@sss.pgh.pa.us
Author(s): Tom Lane

Author: Commitfest Bot

contrib/postgres_fdw/expected/postgres_fdw.out

@@ -3968,18 +3968,19 @@ select c2, sum(c2), count(c2) over (partition by c2%2) from ft2 where c2 < 10 gr
                                                  QUERY PLAN                                                 
 ------------------------------------------------------------------------------------------------------------
  Sort
-   Output: c2, (sum(c2)), (count(c2) OVER (?)), ((c2 % 2))
+   Output: c2, (sum(c2)), (count(c2) OVER w1), ((c2 % 2))
    Sort Key: ft2.c2
    ->  WindowAgg
-         Output: c2, (sum(c2)), count(c2) OVER (?), ((c2 % 2))
+         Output: c2, (sum(c2)), count(c2) OVER w1, ((c2 % 2))
+         Window: w1 AS (PARTITION BY ((ft2.c2 % 2)))
          ->  Sort
                Output: c2, ((c2 % 2)), (sum(c2))
                Sort Key: ((ft2.c2 % 2))
                ->  Foreign Scan
                      Output: c2, ((c2 % 2)), (sum(c2))
                      Relations: Aggregate on (public.ft2)
                      Remote SQL: SELECT c2, (c2 % 2), sum(c2) FROM "S 1"."T 1" WHERE ((c2 < 10)) GROUP BY 1
-(12 rows)
+(13 rows)
 
 select c2, sum(c2), count(c2) over (partition by c2%2) from ft2 where c2 < 10 group by c2 order by 1;
  c2 | sum | count 
@@ -4001,18 +4002,19 @@ select c2, array_agg(c2) over (partition by c2%2 order by c2 desc) from ft1 wher
                                             QUERY PLAN                                             
 ---------------------------------------------------------------------------------------------------
  Sort
-   Output: c2, (array_agg(c2) OVER (?)), ((c2 % 2))
+   Output: c2, (array_agg(c2) OVER w1), ((c2 % 2))
    Sort Key: ft1.c2
    ->  WindowAgg
-         Output: c2, array_agg(c2) OVER (?), ((c2 % 2))
+         Output: c2, array_agg(c2) OVER w1, ((c2 % 2))
+         Window: w1 AS (PARTITION BY ((ft1.c2 % 2)) ORDER BY ft1.c2)
          ->  Sort
                Output: c2, ((c2 % 2))
                Sort Key: ((ft1.c2 % 2)), ft1.c2 DESC
                ->  Foreign Scan
                      Output: c2, ((c2 % 2))
                      Relations: Aggregate on (public.ft1)
                      Remote SQL: SELECT c2, (c2 % 2) FROM "S 1"."T 1" WHERE ((c2 < 10)) GROUP BY 1
-(12 rows)
+(13 rows)
 
 select c2, array_agg(c2) over (partition by c2%2 order by c2 desc) from ft1 where c2 < 10 group by c2 order by 1;
  c2 |  array_agg  
@@ -4031,21 +4033,22 @@ select c2, array_agg(c2) over (partition by c2%2 order by c2 desc) from ft1 wher
 
 explain (verbose, costs off)
 select c2, array_agg(c2) over (partition by c2%2 order by c2 range between current row and unbounded following) from ft1 where c2 < 10 group by c2 order by 1;
-                                            QUERY PLAN                                             
----------------------------------------------------------------------------------------------------
+                                                      QUERY PLAN                                                       
+-----------------------------------------------------------------------------------------------------------------------
  Sort
-   Output: c2, (array_agg(c2) OVER (?)), ((c2 % 2))
+   Output: c2, (array_agg(c2) OVER w1), ((c2 % 2))
    Sort Key: ft1.c2
    ->  WindowAgg
-         Output: c2, array_agg(c2) OVER (?), ((c2 % 2))
+         Output: c2, array_agg(c2) OVER w1, ((c2 % 2))
+         Window: w1 AS (PARTITION BY ((ft1.c2 % 2)) ORDER BY ft1.c2 RANGE BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING)
          ->  Sort
                Output: c2, ((c2 % 2))
                Sort Key: ((ft1.c2 % 2)), ft1.c2
                ->  Foreign Scan
                      Output: c2, ((c2 % 2))
                      Relations: Aggregate on (public.ft1)
                      Remote SQL: SELECT c2, (c2 % 2) FROM "S 1"."T 1" WHERE ((c2 < 10)) GROUP BY 1
-(12 rows)
+(13 rows)
 
 select c2, array_agg(c2) over (partition by c2%2 order by c2 range between current row and unbounded following) from ft1 where c2 < 10 group by c2 order by 1;
  c2 |  array_agg  

src/backend/commands/explain.c

@@ -107,6 +107,11 @@ static void show_sort_group_keys(PlanState *planstate, const char *qlabel,
 								 List *ancestors, ExplainState *es);
 static void show_sortorder_options(StringInfo buf, Node *sortexpr,
 								   Oid sortOperator, Oid collation, bool nullsFirst);
+static void show_window_def(WindowAggState *planstate,
+							List *ancestors, ExplainState *es);
+static void show_window_keys(StringInfo buf, PlanState *planstate,
+							 int nkeys, AttrNumber *keycols,
+							 List *ancestors, ExplainState *es);
 static void show_storage_info(char *maxStorageType, int64 maxSpaceUsed,
 							  ExplainState *es);
 static void show_tablesample(TableSampleClause *tsc, PlanState *planstate,
@@ -2329,12 +2334,13 @@ ExplainNode(PlanState *planstate, List *ancestors,
 										   planstate, es);
 			break;
 		case T_WindowAgg:
+			show_window_def(castNode(WindowAggState, planstate), ancestors, es);
+			show_upper_qual(((WindowAgg *) plan)->runConditionOrig,
+							"Run Condition", planstate, ancestors, es);
 			show_upper_qual(plan->qual, "Filter", planstate, ancestors, es);
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
-			show_upper_qual(((WindowAgg *) plan)->runConditionOrig,
-							"Run Condition", planstate, ancestors, es);
 			show_windowagg_info(castNode(WindowAggState, planstate), es);
 			break;
 		case T_Group:
@@ -3003,6 +3009,113 @@ show_sortorder_options(StringInfo buf, Node *sortexpr,
 	}
 }
 
+/*
+ * Show the window definition for a WindowAgg node.
+ */
+static void
+show_window_def(WindowAggState *planstate, List *ancestors, ExplainState *es)
+{
+	WindowAgg  *wagg = (WindowAgg *) planstate->ss.ps.plan;
+	StringInfoData wbuf;
+	bool		needspace = false;
+
+	initStringInfo(&wbuf);
+	appendStringInfo(&wbuf, "%s AS (", quote_identifier(wagg->winname));
+
+	/* The key columns refer to the tlist of the child plan */
+	ancestors = lcons(wagg, ancestors);
+	if (wagg->partNumCols > 0)
+	{
+		appendStringInfoString(&wbuf, "PARTITION BY ");
+		show_window_keys(&wbuf, outerPlanState(planstate),
+						 wagg->partNumCols, wagg->partColIdx,
+						 ancestors, es);
+		needspace = true;
+	}
+	if (wagg->ordNumCols > 0)
+	{
+		if (needspace)
+			appendStringInfoChar(&wbuf, ' ');
+		appendStringInfoString(&wbuf, "ORDER BY ");
+		show_window_keys(&wbuf, outerPlanState(planstate),
+						 wagg->ordNumCols, wagg->ordColIdx,
+						 ancestors, es);
+		needspace = true;
+	}
+	ancestors = list_delete_first(ancestors);
+	if (wagg->frameOptions & FRAMEOPTION_NONDEFAULT)
+	{
+		List	   *context;
+		bool		useprefix;
+		char	   *framestr;
+
+		/* Set up deparsing context for possible frame expressions */
+		context = set_deparse_context_plan(es->deparse_cxt,
+										   (Plan *) wagg,
+										   ancestors);
+		useprefix = (es->rtable_size > 1 || es->verbose);
+		framestr = get_window_frame_options_for_explain(wagg->frameOptions,
+														wagg->startOffset,
+														wagg->endOffset,
+														context,
+														useprefix);
+		if (needspace)
+			appendStringInfoChar(&wbuf, ' ');
+		appendStringInfoString(&wbuf, framestr);
+		pfree(framestr);
+	}
+	appendStringInfoChar(&wbuf, ')');
+	ExplainPropertyText("Window", wbuf.data, es);
+	pfree(wbuf.data);
+}
+
+/*
+ * Append the keys of a window's PARTITION BY or ORDER BY clause to buf.
+ * We can't use show_sort_group_keys for this because that's too opinionated
+ * about how the result will be displayed.
+ * Note that the "planstate" node should be the WindowAgg's child.
+ */
+static void
+show_window_keys(StringInfo buf, PlanState *planstate,
+				 int nkeys, AttrNumber *keycols,
+				 List *ancestors, ExplainState *es)
+{
+	Plan	   *plan = planstate->plan;
+	List	   *context;
+	bool		useprefix;
+
+	/* Set up deparsing context */
+	context = set_deparse_context_plan(es->deparse_cxt,
+									   plan,
+									   ancestors);
+	useprefix = (es->rtable_size > 1 || es->verbose);
+
+	for (int keyno = 0; keyno < nkeys; keyno++)
+	{
+		/* find key expression in tlist */
+		AttrNumber	keyresno = keycols[keyno];
+		TargetEntry *target = get_tle_by_resno(plan->targetlist,
+											   keyresno);
+		char	   *exprstr;
+
+		if (!target)
+			elog(ERROR, "no tlist entry for key %d", keyresno);
+		/* Deparse the expression, showing any top-level cast */
+		exprstr = deparse_expression((Node *) target->expr, context,
+									 useprefix, true);
+		if (keyno > 0)
+			appendStringInfoString(buf, ", ");
+		appendStringInfoString(buf, exprstr);
+		pfree(exprstr);
+
+		/*
+		 * We don't attempt to provide sort order information because
+		 * WindowAgg carries equality operators not comparison operators;
+		 * compare show_agg_keys.
+		 */
+	}
+}
+
 /*
  * Show information on storage method and maximum memory/disk space used.
  */

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;

src/backend/optimizer/plan/planner.c

@@ -214,6 +214,7 @@ static List *postprocess_setop_tlist(List *new_tlist, List *orig_tlist);
 static void optimize_window_clauses(PlannerInfo *root,
 									WindowFuncLists *wflists);
 static List *select_active_windows(PlannerInfo *root, WindowFuncLists *wflists);
+static void name_active_windows(List *activeWindows);
 static PathTarget *make_window_input_target(PlannerInfo *root,
 											PathTarget *final_target,
 											List *activeWindows);
@@ -1539,7 +1540,11 @@ grouping_planner(PlannerInfo *root, double tuple_fraction,
 				 */
 				optimize_window_clauses(root, wflists);
 
+				/* Extract the list of windows actually in use. */
 				activeWindows = select_active_windows(root, wflists);
+
+				/* Make sure they all have names, for EXPLAIN's use. */
+				name_active_windows(activeWindows);
 			}
 			else
 				parse->hasWindowFuncs = false;
@@ -5914,6 +5919,52 @@ select_active_windows(PlannerInfo *root, WindowFuncLists *wflists)
 	return result;
 }
 
+/*
+ * name_active_windows
+ *	  Ensure all active windows have unique names.
+ *
+ * The parser will have checked that user-assigned window names are unique
+ * within the Query.  Here we assign made-up names to any unnamed
+ * WindowClauses for the benefit of EXPLAIN.  (We don't want to do this
+ * at parse time, because it'd mess up decompilation of views.)
+ *
+ * activeWindows: result of select_active_windows
+ */
+static void
+name_active_windows(List *activeWindows)
+{
+	int			next_n = 1;
+	char		newname[32];
+	ListCell   *lc;
+
+	foreach(lc, activeWindows)
+	{
+		WindowClause *wc = lfirst_node(WindowClause, lc);
+
+		/* Nothing to do if it has a name already. */
+		if (wc->name)
+			continue;
+
+		/* Select a name not currently present in the list. */
+		for (;;)
+		{
+			ListCell   *lc2;
+
+			snprintf(newname, sizeof(newname), "w%d", next_n++);
+			foreach(lc2, activeWindows)
+			{
+				WindowClause *wc2 = lfirst_node(WindowClause, lc2);
+
+				if (wc2->name && strcmp(wc2->name, newname) == 0)
+					break;		/* matched */
+			}
+			if (lc2 == NULL)
+				break;			/* reached the end with no match */
+		}
+		wc->name = pstrdup(newname);
+	}
+}
+
 /*
  * common_prefix_cmp
  *	  QSort comparison function for WindowClauseSortData