Document new ResultReader.Values behavior

CHANGELOG.md

@@ -10,6 +10,8 @@ release work due to releasing multiple packages, and less clear changelogs.
 
 `CommandTag` is now an opaque type instead of directly exposing an underlying `[]byte`.
 
+The return value `ResultReader.Values()` is no longer safe to retain a reference to after a subsequent call to `NextRow()` or `Close()`.
+
 `Trace()` method adds low level message tracing similar to the `PQtrace` function in `libpq`.
 
 pgconn now uses non-blocking IO. This is a significant internal restructuring, but it should not cause any visible changes on its own. However, it is important in implementing other new features.

pgconn/pgconn.go

@@ -1358,8 +1358,7 @@ func (rr *ResultReader) FieldDescriptions() []pgproto3.FieldDescription {
 }
 
 // Values returns the current row data. NextRow must have been previously been called. The returned [][]byte is only
-// valid until the next NextRow call or the ResultReader is closed. However, the underlying byte data is safe to
-// retain a reference to and mutate.
+// valid until the next NextRow call or the ResultReader is closed.
 func (rr *ResultReader) Values() [][]byte {
 	return rr.rowValues
 }