8365815: JFR: Update metadata.xml with 'jfr query' examples

Reviewed-by: mgronlun

make/src/classes/build/tools/jfr/GenerateJfrFiles.java

@@ -922,8 +922,10 @@ public class GenerateJfrFiles {
         }
         out.write("  using JfrEvent<Event" + event.name
                 + ">::commit; // else commit() is hidden by overloaded versions in this class");
-        printConstructor2(out, event, empty);
+        if (!event.fields.isEmpty()) {
-        printCommitMethod(out, event, empty);
+            printConstructor2(out, event, empty);
+            printCommitMethod(out, event, empty);
+        }
         if (!empty) {
             printVerify(out, event.fields);
         }

src/hotspot/share/jfr/metadata/metadata.xml

@@ -40,16 +40,39 @@
          event.commit();
        }
 
+       void baz(char* text) {
+         EventText event;
+         event.set_text(text);
+         event.commit();
+       }
+
        $ make images
        $ java -XX:StartFlightRecording:settings=none,filename=dump.jfr ...
+       $ jfr view Text dump.jfr
+       Time     Event Thread                             Text
+       ======== ======================================== ==========================
+       21:54:29 Attach Listener                          hello
+       21:54:29 Attach Listener                          world
        ...
-       $ jfr print dump.jfr
+       $ jfr query 'SELECT text, COUNT(text) FROM Text GROUP BY text ORDER BY text ASC' dump.jfr
+
+       Text                              Count
+       =================== ===================
+       hello                               622
+       world                                37
+
+       $ jfr query 'SELECT COUNT(duration), AVG(duration), MEDIAN(duration), P90(duration),
+                    P99(duration), P999(duration) FROM Duration' dump.jfr
+
+       The 'jfr query' command is only available in debug builds, but recordings with internal
+       events can be generated by product builds.
 
        Programmatic access:
        try (var rf = new RecordingFile(Path.of("dump.jfr"))) {
            while (rf.hasMoreEvents()) {
                RecordedEvent e = rf.readEvent();
-               System.out.println(e.getName() + " " + e.getDuration());
+               EventType et = e.getEventType();
+               System.out.println(et.getName() + " " + e.getDuration() + " " + e.getValue("text"));
            }
        };
   !-->