Add a flag for table access method to force exclusive write

This commit adds a flag in table access method to force exclusive
write. The feature allows writing of a table, i.e. insert/delete/
update, to be not concurrently safe.

Author: gfphoenix78

src/backend/executor/nodeModifyTable.c

@@ -3186,6 +3186,11 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
 	{
 		resultRelInfo = &mtstate->resultRelInfo[i];
 
+		if (resultRelInfo->ri_RelationDesc->rd_tableam &&
+			(table_scan_flags(resultRelInfo->ri_RelationDesc) & SCAN_FORCE_BIG_WRITE_LOCK))
+		{
+			LockRelation(resultRelInfo->ri_RelationDesc, ExclusiveLock);
+		}
 		/* Let FDWs init themselves for foreign-table result rels */
 		if (!resultRelInfo->ri_usesFdwDirectModify &&
 			resultRelInfo->ri_FdwRoutine != NULL &&

src/include/access/tableam.h

@@ -52,6 +52,9 @@ struct ValidateIndexState;
 */
 #define SCAN_SUPPORT_COLUMN_ORIENTED_SCAN (1 << 0)  /* support column-oriented scanning*/
 
+/* force to held big lock for write */
+#define SCAN_FORCE_BIG_WRITE_LOCK (1 << 1)
+
 /*
  * Bitmask values for the flags argument to the scan_begin callback.
  */