Selectively include window frames in expression walks/mutates.

query_tree_walker and query_tree_mutator were skipping the
windowClause of the query, without regard for the fact that the
startOffset and endOffset in a WindowClause node are expression trees
that need to be processed. This was an oversight in commit ec4be2e
from 2010 which added the expression fields; the main symptom is that
function parameters in window frame clauses don't work in inlined
functions.

Fix (as conservatively as possible since this needs to not break
existing out-of-tree callers) and add tests.

Backpatch all the way, since this has been broken since 9.0.

Per report from Alastair McKinley; fix by me with kibitzing and review
from Tom Lane.

Discussion: https://postgr.es/m/DB6PR0202MB2904E7FDDA9D81504D1E8C68E3800@DB6PR0202MB2904.eurprd02.prod.outlook.com

Author: RhodiumToad

src/backend/catalog/dependency.c

@@ -2214,18 +2214,13 @@ find_expr_references_walker(Node *node,
 							   context->addrs);
 		}
 
-		/* query_tree_walker ignores ORDER BY etc, but we need those opers */
-		find_expr_references_walker((Node *) query->sortClause, context);
-		find_expr_references_walker((Node *) query->groupClause, context);
-		find_expr_references_walker((Node *) query->windowClause, context);
-		find_expr_references_walker((Node *) query->distinctClause, context);
-
 		/* Examine substructure of query */
 		context->rtables = lcons(query->rtable, context->rtables);
 		result = query_tree_walker(query,
 								   find_expr_references_walker,
 								   (void *) context,
-								   QTW_IGNORE_JOINALIASES);
+								   QTW_IGNORE_JOINALIASES |
+								   QTW_EXAMINE_SORTGROUP);
 		context->rtables = list_delete_first(context->rtables);
 		return result;
 	}

src/backend/nodes/nodeFuncs.c

@@ -2278,6 +2278,13 @@ query_tree_walker(Query *query,
 {
 	Assert(query != NULL && IsA(query, Query));
 
+	/*
+	 * We don't walk any utilityStmt here. However, we can't easily assert
+	 * that it is absent, since there are at least two code paths by which
+	 * action statements from CREATE RULE end up here, and NOTIFY is allowed
+	 * in a rule action.
+	 */
+
 	if (walker((Node *) query->targetList, context))
 		return true;
 	if (walker((Node *) query->withCheckOptions, context))
@@ -2296,6 +2303,54 @@ query_tree_walker(Query *query,
 		return true;
 	if (walker(query->limitCount, context))
 		return true;
+
+	/*
+	 * Most callers aren't interested in SortGroupClause nodes since those
+	 * don't contain actual expressions. However they do contain OIDs which
+	 * may be needed by dependency walkers etc.
+	 */
+	if ((flags & QTW_EXAMINE_SORTGROUP))
+	{
+		if (walker((Node *) query->groupClause, context))
+			return true;
+		if (walker((Node *) query->windowClause, context))
+			return true;
+		if (walker((Node *) query->sortClause, context))
+			return true;
+		if (walker((Node *) query->distinctClause, context))
+			return true;
+	}
+	else
+	{
+		/*
+		 * But we need to walk the expressions under WindowClause nodes even
+		 * if we're not interested in SortGroupClause nodes.
+		 */
+		ListCell   *lc;
+
+		foreach(lc, query->windowClause)
+		{
+			WindowClause *wc = lfirst_node(WindowClause, lc);
+
+			if (walker(wc->startOffset, context))
+				return true;
+			if (walker(wc->endOffset, context))
+				return true;
+		}
+	}
+
+	/*
+	 * groupingSets and rowMarks are not walked:
+	 *
+	 * groupingSets contain only ressortgrouprefs (integers) which are
+	 * meaningless without the corresponding groupClause or tlist.
+	 * Accordingly, any walker that needs to care about them needs to handle
+	 * them itself in its Query processing.
+	 *
+	 * rowMarks is not walked because it contains only rangetable indexes (and
+	 * flags etc.) and therefore should be handled at Query level similarly.
+	 */
+
 	if (!(flags & QTW_IGNORE_CTE_SUBQUERIES))
 	{
 		if (walker((Node *) query->cteList, context))
@@ -3153,6 +3208,56 @@ query_tree_mutator(Query *query,
 	MUTATE(query->havingQual, query->havingQual, Node *);
 	MUTATE(query->limitOffset, query->limitOffset, Node *);
 	MUTATE(query->limitCount, query->limitCount, Node *);
+
+	/*
+	 * Most callers aren't interested in SortGroupClause nodes since those
+	 * don't contain actual expressions. However they do contain OIDs, which
+	 * may be of interest to some mutators.
+	 */
+
+	if ((flags & QTW_EXAMINE_SORTGROUP))
+	{
+		MUTATE(query->groupClause, query->groupClause, List *);
+		MUTATE(query->windowClause, query->windowClause, List *);
+		MUTATE(query->sortClause, query->sortClause, List *);
+		MUTATE(query->distinctClause, query->distinctClause, List *);
+	}
+	else
+	{
+		/*
+		 * But we need to mutate the expressions under WindowClause nodes even
+		 * if we're not interested in SortGroupClause nodes.
+		 */
+		List	   *resultlist;
+		ListCell   *temp;
+
+		resultlist = NIL;
+		foreach(temp, query->windowClause)
+		{
+			WindowClause *wc = lfirst_node(WindowClause, temp);
+			WindowClause *newnode;
+
+			FLATCOPY(newnode, wc, WindowClause);
+			MUTATE(newnode->startOffset, wc->startOffset, Node *);
+			MUTATE(newnode->endOffset, wc->endOffset, Node *);
+
+			resultlist = lappend(resultlist, (Node *) newnode);
+		}
+		query->windowClause = resultlist;
+	}
+
+	/*
+	 * groupingSets and rowMarks are not mutated:
+	 *
+	 * groupingSets contain only ressortgroup refs (integers) which are
+	 * meaningless without the groupClause or tlist. Accordingly, any mutator
+	 * that needs to care about them needs to handle them itself in its Query
+	 * processing.
+	 *
+	 * rowMarks contains only rangetable indexes (and flags etc.) and
+	 * therefore should be handled at Query level similarly.
+	 */
+
 	if (!(flags & QTW_IGNORE_CTE_SUBQUERIES))
 		MUTATE(query->cteList, query->cteList, List *);
 	else						/* else copy CTE list as-is */

src/include/nodes/nodeFuncs.h

@@ -27,6 +27,7 @@
 #define QTW_EXAMINE_RTES_AFTER		0x20	/* examine RTE nodes after their
 											 * contents */
 #define QTW_DONT_COPY_QUERY			0x40	/* do not copy top Query */
+#define QTW_EXAMINE_SORTGROUP		0x80	/* include SortGroupNode lists */
 
 /* callback function for check_functions_in_node */
 typedef bool (*check_function_callback) (Oid func_id, void *context);

src/test/regress/expected/window.out

@@ -3821,3 +3821,45 @@ SELECT i, b, bool_and(b) OVER w, bool_or(b) OVER w
  5 | t | t        | t
 (5 rows)
 
+-- Tests for problems with failure to walk or mutate expressions
+-- within window frame clauses.
+-- test walker (fails with collation error if expressions are not walked)
+SELECT array_agg(i) OVER w
+  FROM generate_series(1,5) i
+WINDOW w AS (ORDER BY i ROWS BETWEEN (('foo' < 'foobar')::integer) PRECEDING AND CURRENT ROW);
+ array_agg 
+-----------
+ {1}
+ {1,2}
+ {2,3}
+ {3,4}
+ {4,5}
+(5 rows)
+
+-- test mutator (fails when inlined if expressions are not mutated)
+CREATE FUNCTION pg_temp.f(group_size BIGINT) RETURNS SETOF integer[]
+AS $$
+    SELECT array_agg(s) OVER w
+      FROM generate_series(1,5) s
+    WINDOW w AS (ORDER BY s ROWS BETWEEN CURRENT ROW AND GROUP_SIZE FOLLOWING)
+$$ LANGUAGE SQL STABLE;
+EXPLAIN (costs off) SELECT * FROM pg_temp.f(2);
+                      QUERY PLAN                      
+------------------------------------------------------
+ Subquery Scan on f
+   ->  WindowAgg
+         ->  Sort
+               Sort Key: s.s
+               ->  Function Scan on generate_series s
+(5 rows)
+
+SELECT * FROM pg_temp.f(2);
+    f    
+---------
+ {1,2,3}
+ {2,3,4}
+ {3,4,5}
+ {4,5}
+ {5}
+(5 rows)
+

src/test/regress/sql/window.sql

@@ -1257,3 +1257,22 @@ SELECT to_char(SUM(n::float8) OVER (ORDER BY i ROWS BETWEEN CURRENT ROW AND 1 FO
 SELECT i, b, bool_and(b) OVER w, bool_or(b) OVER w
   FROM (VALUES (1,true), (2,true), (3,false), (4,false), (5,true)) v(i,b)
   WINDOW w AS (ORDER BY i ROWS BETWEEN CURRENT ROW AND 1 FOLLOWING);
+
+-- Tests for problems with failure to walk or mutate expressions
+-- within window frame clauses.
+
+-- test walker (fails with collation error if expressions are not walked)
+SELECT array_agg(i) OVER w
+  FROM generate_series(1,5) i
+WINDOW w AS (ORDER BY i ROWS BETWEEN (('foo' < 'foobar')::integer) PRECEDING AND CURRENT ROW);
+
+-- test mutator (fails when inlined if expressions are not mutated)
+CREATE FUNCTION pg_temp.f(group_size BIGINT) RETURNS SETOF integer[]
+AS $$
+    SELECT array_agg(s) OVER w
+      FROM generate_series(1,5) s
+    WINDOW w AS (ORDER BY s ROWS BETWEEN CURRENT ROW AND GROUP_SIZE FOLLOWING)
+$$ LANGUAGE SQL STABLE;
+
+EXPLAIN (costs off) SELECT * FROM pg_temp.f(2);
+SELECT * FROM pg_temp.f(2);