修复了group by后面不能加rownum（或别名）的bug以及where后面接rownum的别名的报错信息

src/common/backend/nodes/equalfuncs.cpp

@@ -2432,6 +2432,14 @@ static bool _equalDropSynonymStmt(DropSynonymStmt* a, DropSynonymStmt* b)
     return true;
 }
 
+static bool _equalRownum(Rownum* a, Rownum* b)
+{
+    COMPARE_SCALAR_FIELD(rownumcollid);
+    COMPARE_LOCATION_FIELD(location);
+
+    return true;
+}
+
 /*
  * Stuff from pg_list.h
  */
@@ -3428,6 +3436,9 @@ bool equal(const void* a, const void* b)
         case T_DropSynonymStmt:
             retval = _equalDropSynonymStmt((DropSynonymStmt*)a, (DropSynonymStmt*)b);
             break;
+        case T_Rownum:
+            retval = _equalRownum((Rownum*)a, (Rownum*)b);
+            break;
 
         default:
             ereport(ERROR,

src/common/backend/parser/parse_expr.cpp

@@ -444,7 +444,11 @@ static Node* replaceExprAliasIfNecessary(ParseState* pstate, char* colname, Colu
                     (errcode(ERRCODE_UNDEFINED_COLUMN),
                         errmsg("Alias \"%s\" reference with window function included is not supported.", colname),
                         parser_errposition(pstate, cref->location)));
-
+            } else if (contain_rownum_expr((Node*)tle->expr)) {
+                ereport(ERROR,
+                    (errcode(ERRCODE_UNDEFINED_COLUMN),
+                     errmsg("Alias \"%s\" reference with ROWNUM included is invalid.", colname),
+                     parser_errposition(pstate, cref->location)));
             } else if (contain_volatile_functions((Node*)tle->expr)) {
                 ereport(ERROR,
                     (errcode(ERRCODE_UNDEFINED_COLUMN),

src/include/optimizer/clauses.h

@@ -106,6 +106,12 @@ extern List* extract_function_outarguments(Oid funcid, List* parameters, List* f
 extern bool need_adjust_agg_inner_func_type(Aggref* aggref);
 
 extern bool contain_rownum_walker(Node *node, void *context); 
+
+static inline bool contain_rownum_expr(Node *node) 
+{
+    return contain_rownum_walker(node, NULL);
+}
+
 extern List* get_quals_lists(Node *jtnode);
 
 #endif /* CLAUSES_H */

src/test/regress/expected/xc_rownum.out

@@ -211,7 +211,47 @@ select rownum, name from (select name from distributors where rownum <= 4 inters
       2 | westward
 (2 rows)
 
+--test group by
+select rownum from distributors group by rownum;
+ rownum 
+--------
+      3
+      1
+      2
+      4
+(4 rows)
 
+select rownum rn from distributors group by rn;
+ rn 
+----
+  3
+  1
+  2
+  4
+(4 rows)
+
+select rownum + 1 from dual group by rownum;
+ ?column? 
+----------
+        2
+(1 row)
+
+select rownum + 1 rn from dual group by rn;
+ rn 
+----
+  2
+(1 row)
+
+--test alias name after where
+select rownum rn, name from distributors where rn<3;
+ERROR:  Alias "rn" reference with ROWNUM included is invalid.
+LINE 1: select rownum rn, name from distributors where rn<3;
+                                                       ^
+select rownum rowno2, * from (select rownum rowno1, * from distributors order by id desc) where rowno2 < 2;
+ERROR:  Alias "rowno2" reference with ROWNUM included is invalid.
+LINE 1: ...wno1, * from distributors order by id desc) where rowno2 < 2...
+                                                             ^
+															 
 --test except and minus
 --create test table
 create table except_table (a int, b int);

src/test/regress/sql/xc_rownum.sql

@@ -80,6 +80,14 @@ select rownum, name from (select name from distributors intersect all select nam
 select rownum, name from (select name from distributors intersect all select name from actors order by 1) as result where rownum < 3;
 select rownum, name from (select name from distributors intersect all select name from actors order by 1) as result where rownum < 6;
 select rownum, name from (select name from distributors where rownum <= 4 intersect all select name from actors where rownum <= 4 order by 1) as result;
+--test group by
+select rownum from distributors group by rownum;
+select rownum rn from distributors group by rn;
+select rownum + 1 from dual group by rownum;
+select rownum + 1 rn from dual group by rn;
+--test alias name after where
+select rownum rn, name from distributors where rn<3;
+select rownum rowno2, * from (select rownum rowno1, * from distributors order by id desc) where rowno2 < 2;
 
 --test except and minus
 --create test table