diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index ac5ce071d1..711adc4622 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -3365,6 +3365,10 @@ AbortCurrentTransaction(void)
  *	a transaction block, typically because they have non-rollback-able
  *	side effects or do internal commits.
  *
+ *	If this routine completes successfully, then the calling statement is
+ *	guaranteed that if it completes without error, its results will be
+ *	committed immediately.
+ *
  *	If we have already started a transaction block, issue an error; also issue
  *	an error if we appear to be running inside a user-defined function (which
  *	could issue more commands and possibly cause a failure after the statement
@@ -3490,6 +3494,10 @@ CheckTransactionBlock(bool isTopLevel, bool throwError, const char *stmtType)
  *	a transaction block than when running as single commands.  ANALYZE is
  *	currently the only example.
  *
+ *	If this routine returns "false", then the calling statement is
+ *	guaranteed that if it completes without error, its results will be
+ *	committed immediately.
+ *
  *	isTopLevel: passed down from ProcessUtility to determine whether we are
  *	inside a function.
  */