diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 50f092d7eb..ee9f0fafdd 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -3455,6 +3455,10 @@ AbortCurrentTransaction(void)
  *
  *	We must also set XACT_FLAGS_NEEDIMMEDIATECOMMIT in MyXactFlags, to ensure
  *	that postgres.c follows through by committing after the statement is done.
+ *	This ensures that the statement that calls this function never be rolled
+ *	back if it finishes successfully. Note that if there are preceding statements
+ *	in a pipeline, they are committed in the same transaction of the current
+ *	statement.
  *
  *	isTopLevel: passed down from ProcessUtility to determine whether we are
  *	inside a function.  (We will always fail if this is false, but it's
@@ -3573,6 +3577,10 @@ CheckTransactionBlock(bool isTopLevel, bool throwError, const char *stmtType)
  *	a transaction block than when running as single commands.  ANALYZE is
  *	currently the only example.
  *
+ *	Returning false ensures that the statement that calls this function never
+ *	be rolled back if it finishes successfully. See comments on
+ *	PreventInTransactionBlock.
+ *
  *	isTopLevel: passed down from ProcessUtility to determine whether we are
  *	inside a function.
  */