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 ec4be2ee6
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

2 files changed, 61 insertions, 0 deletions

diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index edc93d5729..d5fd4045f9 100644
--- a/src/test/regress/expected/window.out
+++ b/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)
+
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index fc6d4cc903..fe273aa31e 100644
--- a/src/test/regress/sql/window.sql
+++ b/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);