diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index e3dbc4b5ea..4fe872290a 100644
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -1730,10 +1730,10 @@ SELECT string_agg(a ORDER BY a, ',') FROM table; -- incorrect
The syntax of a window function call is one of the following:
-function_name (expression , expression ... ) [ FILTER ( WHERE filter_clause ) ] OVER ( window_definition )
function_name (expression , expression ... ) [ FILTER ( WHERE filter_clause ) ] OVER window_name
-function_name ( * ) [ FILTER ( WHERE filter_clause ) ] OVER ( window_definition )
+function_name (expression , expression ... ) [ FILTER ( WHERE filter_clause ) ] OVER ( window_definition )
function_name ( * ) [ FILTER ( WHERE filter_clause ) ] OVER window_name
+function_name ( * ) [ FILTER ( WHERE filter_clause ) ] OVER ( window_definition )
where window_definition
has the syntax
@@ -1768,15 +1768,14 @@ UNBOUNDED FOLLOWING
window_name is a reference to a named window
specification defined in the query's WINDOW clause.
- Named window specifications are usually referenced with just
- OVER window_name, but it is
- also possible to write a window name inside the parentheses and then
- optionally supply an ordering clause and/or frame clause (the referenced
- window must lack these clauses, if they are supplied here).
- This latter syntax follows the same rules as modifying an existing
- window name within the WINDOW clause; see the
- reference
- page for details.
+ Alternatively, a full window_definition can
+ be given within parentheses, using the same syntax as for defining a
+ named window in the WINDOW clause; see the
+ reference page for details. It's worth
+ pointing out that OVER wname is not exactly equivalent to
+ OVER (wname); the latter implies copying and modifying the
+ window definition, and will be rejected if the referenced window
+ specification includes a frame clause.
@@ -1853,12 +1852,19 @@ UNBOUNDED FOLLOWING
PRECEDING is not allowed.
+
+ If FILTER is specified, then only the input
+ rows for which the filter_clause
+ evaluates to true are fed to the window function; other rows
+ are discarded. Only aggregate window functions accept
+ a FILTER clause.
+
+
The built-in window functions are described in . Other window functions can be added by
the user. Also, any built-in or user-defined aggregate function can be
- used as a window function. Only aggregate window functions accept
- a FILTER clause.
+ used as a window function.
diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index ea90e58f71..1f6306a7d3 100644
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -1735,11 +1735,16 @@ transformWindowDefinitions(ParseState *pstate,
/*
* Per spec, a windowdef that references a previous one copies the
* previous partition clause (and mustn't specify its own). It can
- * specify its own ordering clause. but only if the previous one had
+ * specify its own ordering clause, but only if the previous one had
* none. It always specifies its own frame clause, and the previous
- * one must not have a frame clause. (Yeah, it's bizarre that each of
+ * one must not have a frame clause. Yeah, it's bizarre that each of
* these cases works differently, but SQL:2008 says so; see 7.11
- * syntax rule 10 and general rule 1.)
+ * syntax rule 10 and general rule 1. The frame
+ * clause rule is especially bizarre because it makes "OVER foo"
+ * different from "OVER (foo)", and requires the latter to throw an
+ * error if foo has a nondefault frame clause. Well, ours not to
+ * reason why, but we do go out of our way to throw a useful error
+ * message for such cases.
*/
if (refwc)
{
@@ -1778,11 +1783,27 @@ transformWindowDefinitions(ParseState *pstate,
wc->copiedOrder = false;
}
if (refwc && refwc->frameOptions != FRAMEOPTION_DEFAULTS)
+ {
+ /*
+ * Use this message if this is a WINDOW clause, or if it's an OVER
+ * clause that includes ORDER BY or framing clauses. (We already
+ * rejected PARTITION BY above, so no need to check that.)
+ */
+ if (windef->name ||
+ orderClause || windef->frameOptions != FRAMEOPTION_DEFAULTS)
+ ereport(ERROR,
+ (errcode(ERRCODE_WINDOWING_ERROR),
+ errmsg("cannot copy window \"%s\" because it has a frame clause",
+ windef->refname),
+ parser_errposition(pstate, windef->location)));
+ /* Else this clause is just OVER (foo), so say this: */
ereport(ERROR,
(errcode(ERRCODE_WINDOWING_ERROR),
- errmsg("cannot override frame clause of window \"%s\"",
- windef->refname),
+ errmsg("cannot copy window \"%s\" because it has a frame clause",
+ windef->refname),
+ errhint("Omit the parentheses in this OVER clause."),
parser_errposition(pstate, windef->location)));
+ }
wc->frameOptions = windef->frameOptions;
/* Process frame offset expressions */
wc->startOffset = transformFrameOffset(pstate, wc->frameOptions,