1 files changed, 69 insertions, 0 deletions
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 6723f46f3f1..23190e1af05 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -138,6 +138,8 @@ typedef struct Query
 
 	List	   *groupClause;	/* a list of SortGroupClause's */
 
+	List	   *groupingSets;	/* a list of GroupingSet's if present */
+
 	Node	   *havingQual;		/* qualifications applied to groups */
 
 	List	   *windowClause;	/* a list of WindowClause's */
@@ -1002,6 +1004,73 @@ typedef struct SortGroupClause
 } SortGroupClause;
 
 /*
+ * GroupingSet -
+ *		representation of CUBE, ROLLUP and GROUPING SETS clauses
+ *
+ * In a Query with grouping sets, the groupClause contains a flat list of
+ * SortGroupClause nodes for each distinct expression used.  The actual
+ * structure of the GROUP BY clause is given by the groupingSets tree.
+ *
+ * In the raw parser output, GroupingSet nodes (of all types except SIMPLE
+ * which is not used) are potentially mixed in with the expressions in the
+ * groupClause of the SelectStmt.  (An expression can't contain a GroupingSet,
+ * but a list may mix GroupingSet and expression nodes.)  At this stage, the
+ * content of each node is a list of expressions, some of which may be RowExprs
+ * which represent sublists rather than actual row constructors, and nested
+ * GroupingSet nodes where legal in the grammar.  The structure directly
+ * reflects the query syntax.
+ *
+ * In parse analysis, the transformed expressions are used to build the tlist
+ * and groupClause list (of SortGroupClause nodes), and the groupingSets tree
+ * is eventually reduced to a fixed format:
+ *
+ * EMPTY nodes represent (), and obviously have no content
+ *
+ * SIMPLE nodes represent a list of one or more expressions to be treated as an
+ * atom by the enclosing structure; the content is an integer list of
+ * ressortgroupref values (see SortGroupClause)
+ *
+ * CUBE and ROLLUP nodes contain a list of one or more SIMPLE nodes.
+ *
+ * SETS nodes contain a list of EMPTY, SIMPLE, CUBE or ROLLUP nodes, but after
+ * parse analysis they cannot contain more SETS nodes; enough of the syntactic
+ * transforms of the spec have been applied that we no longer have arbitrarily
+ * deep nesting (though we still preserve the use of cube/rollup).
+ *
+ * Note that if the groupingSets tree contains no SIMPLE nodes (only EMPTY
+ * nodes at the leaves), then the groupClause will be empty, but this is still
+ * an aggregation query (similar to using aggs or HAVING without GROUP BY).
+ *
+ * As an example, the following clause:
+ *
+ * GROUP BY GROUPING SETS ((a,b), CUBE(c,(d,e)))
+ *
+ * looks like this after raw parsing:
+ *
+ * SETS( RowExpr(a,b) , CUBE( c, RowExpr(d,e) ) )
+ *
+ * and parse analysis converts it to:
+ *
+ * SETS( SIMPLE(1,2), CUBE( SIMPLE(3), SIMPLE(4,5) ) )
+ */
+typedef enum
+{
+	GROUPING_SET_EMPTY,
+	GROUPING_SET_SIMPLE,
+	GROUPING_SET_ROLLUP,
+	GROUPING_SET_CUBE,
+	GROUPING_SET_SETS
+} GroupingSetKind;
+
+typedef struct GroupingSet
+{
+	NodeTag		type;
+	GroupingSetKind kind;
+	List	   *content;
+	int			location;
+} GroupingSet;
+
+/*
  * WindowClause -
  *		transformed representation of WINDOW and OVER clauses
  *