1 files changed, 35 insertions, 0 deletions
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 4a4dd7e9ef8..a5467c53799 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -272,6 +272,41 @@ typedef struct Aggref
 } Aggref;
 
 /*
+ * GroupingFunc
+ *
+ * A GroupingFunc is a GROUPING(...) expression, which behaves in many ways
+ * like an aggregate function (e.g. it "belongs" to a specific query level,
+ * which might not be the one immediately containing it), but also differs in
+ * an important respect: it never evaluates its arguments, they merely
+ * designate expressions from the GROUP BY clause of the query level to which
+ * it belongs.
+ *
+ * The spec defines the evaluation of GROUPING() purely by syntactic
+ * replacement, but we make it a real expression for optimization purposes so
+ * that one Agg node can handle multiple grouping sets at once.  Evaluating the
+ * result only needs the column positions to check against the grouping set
+ * being projected.  However, for EXPLAIN to produce meaningful output, we have
+ * to keep the original expressions around, since expression deparse does not
+ * give us any feasible way to get at the GROUP BY clause.
+ *
+ * Also, we treat two GroupingFunc nodes as equal if they have equal arguments
+ * lists and agglevelsup, without comparing the refs and cols annotations.
+ *
+ * In raw parse output we have only the args list; parse analysis fills in the
+ * refs list, and the planner fills in the cols list.
+ */
+typedef struct GroupingFunc
+{
+	Expr		xpr;
+	List	   *args;			/* arguments, not evaluated but kept for
+								 * benefit of EXPLAIN etc. */
+	List	   *refs;			/* ressortgrouprefs of arguments */
+	List	   *cols;			/* actual column positions set by planner */
+	Index		agglevelsup;	/* same as Aggref.agglevelsup */
+	int			location;		/* token location */
+} GroupingFunc;
+
+/*
  * WindowFunc
  */
 typedef struct WindowFunc