H2 Console: new built-in command @sleep to help profile another session.

h2/src/docsrc/html/tutorial.html

@@ -384,6 +384,17 @@ otherwise they are not parsed correctly. If in doubt, add ';' before the command
             (if there are 3).
         </td>
     </tr>
+    <tr>
+        <td class="notranslate">
+            @prof_stop;<br />
+            @sleep 10;<br />
+            @prof_stop;
+        </td>
+        <td>
+            Sleep for a number of seconds. Used to profile a long running query or 
+            operation that is running in another session (but in the same process).
+        </td>
+    </tr>
     <tr>
         <td class="notranslate">
             @transaction_isolation;<br />

h2/src/main/org/h2/server/web/WebApp.java

@@ -1277,6 +1277,14 @@ public class WebApp {
                 profiler = new Profiler();
                 profiler.startCollecting();
                 return "Ok";
+            } else if (isBuiltIn(sql, "@sleep")) {
+                String s = sql.substring("@sleep".length()).trim();
+                int sleep = 1;
+                if (s.length() > 0) {
+                    sleep = Integer.parseInt(s);
+                }
+                Thread.sleep(sleep * 1000);
+                return "Ok";
             } else if (isBuiltIn(sql, "@transaction_isolation")) {
                 String s = sql.substring("@transaction_isolation".length()).trim();
                 if (s.length() > 0) {