Add new callback 'scan_flags' for table access method

The table access method supports different features due to the different
implementation, this callback is used to indicate what the AM can do,
what features the AM can support.

src/backend/access/aocs/aocsam_handler.c

@@ -757,6 +757,12 @@ aoco_getnextslot(TableScanDesc scan, ScanDirection direction, TupleTableSlot *sl
 	return false;
 }
 
+static int
+aoco_scan_flags(Relation rel)
+{
+	return 0;
+}
+
 static Size
 aoco_parallelscan_estimate(Relation rel)
 {
@@ -2402,6 +2408,7 @@ static TableAmRoutine ao_column_methods = {
 	.scan_end = aoco_endscan,
 	.scan_rescan = aoco_rescan,
 	.scan_getnextslot = aoco_getnextslot,
+	.scan_flags = aoco_scan_flags,
 
 	.parallelscan_estimate = aoco_parallelscan_estimate,
 	.parallelscan_initialize = aoco_parallelscan_initialize,

src/backend/access/appendonly/appendonlyam.c

@@ -1799,6 +1799,12 @@ appendonly_getnextslot(TableScanDesc scan, ScanDirection direction, TupleTableSl
 	return false;
 }
 
+int
+appendonly_scan_flags(Relation relation)
+{
+	return 0;
+}
+
 static void
 closeFetchSegmentFile(AppendOnlyFetchDesc aoFetchDesc)
 {

src/backend/access/appendonly/appendonlyam_handler.c

@@ -2345,6 +2345,7 @@ static const TableAmRoutine ao_row_methods = {
 	.scan_end = appendonly_endscan,
 	.scan_rescan = appendonly_rescan,
 	.scan_getnextslot = appendonly_getnextslot,
+	.scan_flags = appendonly_scan_flags,
 
 	.parallelscan_estimate = appendonly_parallelscan_estimate,
 	.parallelscan_initialize = appendonly_parallelscan_initialize,

src/backend/access/heap/heapam.c

@@ -1621,6 +1621,12 @@ heap_getnextslot_tidrange(TableScanDesc sscan, ScanDirection direction,
 	return true;
 }
 
+int
+heap_scan_flags(Relation relation)
+{
+	return 0;
+}
+
 /*
  *	heap_fetch		- retrieve tuple with given tid
  *

src/backend/access/heap/heapam_handler.c

@@ -2597,6 +2597,7 @@ static const TableAmRoutine heapam_methods = {
 
 	.scan_set_tidrange = heap_set_tidrange,
 	.scan_getnextslot_tidrange = heap_getnextslot_tidrange,
+	.scan_flags = heap_scan_flags,
 
 	.parallelscan_estimate = table_block_parallelscan_estimate,
 	.parallelscan_initialize = table_block_parallelscan_initialize,

src/include/access/heapam.h

@@ -135,6 +135,7 @@ extern void heap_set_tidrange(TableScanDesc sscan, ItemPointer mintid,
 extern bool heap_getnextslot_tidrange(TableScanDesc sscan,
 									  ScanDirection direction,
 									  TupleTableSlot *slot);
+extern int heap_scan_flags(Relation relation);
 extern bool heap_fetch(Relation relation, Snapshot snapshot,
 					   HeapTuple tuple, Buffer *userbuf);
 extern bool heap_fetch_extended(Relation relation, Snapshot snapshot,

src/include/cdb/cdbappendonlyam.h

@@ -445,6 +445,7 @@ extern void appendonly_endscan(TableScanDesc scan);
 extern bool appendonly_getnextslot(TableScanDesc scan,
 								   ScanDirection direction,
 								   TupleTableSlot *slot);
+extern int appendonly_scan_flags(Relation relation);
 extern AppendOnlyFetchDesc appendonly_fetch_init(
 	Relation 	relation,
 	Snapshot    snapshot,