Checking ao table while looking for column to prevent finding invalid…

… system columns

add check for ao table while looking for column

add tests

add comments

src/backend/parser/parse_relation.c

@@ -531,6 +531,20 @@ GetCTEForRTE(ParseState *pstate, RangeTblEntry *rte, int rtelevelsup)
 	return NULL;				/* keep compiler quiet */
 }
 
+static bool
+IsAppendOptimizedByOid(Oid relid)
+{
+	Relation	rel;
+	bool		result;
+
+	rel = heap_open(relid, NoLock);
+
+	result = RelationIsAppendOptimized(rel);
+	heap_close(rel, NoLock);
+
+	return result;
+}
+
 /*
  * scanRTEForColumn
  *	  Search the column names of a single RTE for the given name.
@@ -603,6 +617,12 @@ scanRTEForColumn(ParseState *pstate, RangeTblEntry *rte, char *colname,
 			Gp_role != GP_ROLE_UTILITY)
 			return result;
 
+		/* In GPDB tables that have append-optimized storage system columns are not
+		 * stored in tuples, so we check it here
+		 */
+		if (IsAppendOptimizedByOid(rte->relid))
+			return result;
+
 		/* quick check to see if name could be a system column */
 		attnum = specialAttNum(colname);
 

src/test/regress/input/appendonly.source

@@ -804,3 +804,8 @@ insert into fix_ao_truncate_last_sequence select 1, 1 from generate_series(1, 5)
 select count(*) from fix_ao_truncate_last_sequence;
 abort;
 
+-- Check if system columns in ao table can be selected
+DROP TABLE IF EXISTS ttt_ao;
+CREATE TABLE ttt (id int) WITH (appendonly=true) DISTRIBUTED BY (id);
+INSERT INTO ttt VALUES(1);
+SELECT xmin FROM ttt;

src/test/regress/output/appendonly.source

@@ -1706,3 +1706,12 @@ select count(*) from fix_ao_truncate_last_sequence;
 (1 row)
 
 abort;
+
+-- Check if system columns in ao table can be selected
+DROP TABLE IF EXISTS ttt_ao;
+CREATE TABLE ttt (id int) WITH (appendonly=true) DISTRIBUTED BY (id);
+INSERT INTO ttt VALUES(1);
+SELECT xmin FROM ttt;
+ERROR:  column "xmin" does not exist
+LINE 1: select xmin from ttt;
+               ^