perf: execute "SET application_name" if name has changed only

This improves cases when application is setting the same name again and again (e.g. glassfish3).

See http://www.postgresql.org/message-id/flat/CADK3HHJKRq09otwqtv3rtnDh9h_LqFvBz+BHKgHjZgtnybvF1g@mail.gmail.com

closes #537

pgjdbc/src/main/java/org/postgresql/core/ProtocolConnection.java

@@ -186,4 +186,10 @@ public interface ProtocolConnection {
    * @return backend timezone in java format.
    */
   TimeZone getTimeZone();
+
+  /**
+   * Returns application_name connection property.
+   * @return application_name connection property
+   */
+  String getApplicationName();
 }

pgjdbc/src/main/java/org/postgresql/core/v2/ProtocolConnectionImpl.java

@@ -234,6 +234,11 @@ public TimeZone getTimeZone() {
     return TimeZone.getDefault();
   }
 
+  @Override
+  public String getApplicationName() {
+    return "";
+  }
+
   private String serverVersion;
   private int serverVersionNum = 0;
   private int cancelPid;

pgjdbc/src/main/java/org/postgresql/core/v3/ProtocolConnectionImpl.java

@@ -245,6 +245,18 @@ public TimeZone getTimeZone() {
     return timeZone;
   }
 
+  void setApplicationName(String applicationName) {
+    this.applicationName = applicationName;
+  }
+
+  @Override
+  public String getApplicationName() {
+    if (applicationName == null) {
+      return "";
+    }
+    return applicationName;
+  }
+
   /**
    * True if server uses integers for date and time fields. False if server uses double.
    */
@@ -279,4 +291,9 @@ public TimeZone getTimeZone() {
    * TimeZone of the current connection (TimeZone backend parameter)
    */
   private TimeZone timeZone;
+
+  /**
+   * application_name connection property
+   */
+  private String applicationName;
 }

pgjdbc/src/main/java/org/postgresql/core/v3/QueryExecutorImpl.java

@@ -2091,6 +2091,9 @@ protected void processResults(ResultHandler handler, int flags) throws IOExcepti
           if ("TimeZone".equals(name)) {
             protoConnection.setTimeZone(TimestampUtils.parseBackendTimeZone(value));
           }
+          if ("application_name".equals(name)) {
+            protoConnection.setApplicationName(value);
+          }
           break;
         }
 

pgjdbc/src/main/java/org/postgresql/jdbc/PgConnection.java

@@ -1385,6 +1385,10 @@ public void setClientInfo(String name, String value) throws SQLClientInfoExcepti
       if (value == null) {
         value = "";
       }
+      final String oldValue = protoConnection.getApplicationName();
+      if (value.equals(oldValue)) {
+        return;
+      }
 
       try {
         StringBuilder sql = new StringBuilder("SET application_name = '");
@@ -1435,11 +1439,13 @@ public void setClientInfo(Properties properties) throws SQLClientInfoException {
 
   public String getClientInfo(String name) throws SQLException {
     checkClosed();
+    _clientInfo.put("ApplicationName", protoConnection.getApplicationName());
     return _clientInfo.getProperty(name);
   }
 
   public Properties getClientInfo() throws SQLException {
     checkClosed();
+    _clientInfo.put("ApplicationName", protoConnection.getApplicationName());
     return _clientInfo;
   }
 

pgjdbc/src/test/java/org/postgresql/test/jdbc4/ClientInfoTest.java

@@ -56,6 +56,22 @@ public void testSetAppName() throws SQLException {
     assertEquals("my app", _conn.getClientInfo().getProperty("ApplicationName"));
   }
 
+  public void testExplicitSetAppNameNotificationIsParsed() throws SQLException {
+    if (!TestUtil.haveMinimumServerVersion(_conn, "9.0")) {
+      return;
+    }
+
+    String appName = "test-42";
+
+    Statement s = _conn.createStatement();
+    s.execute("set application_name='" + appName + "'");
+    s.close();
+    assertEquals("application_name was set to " + appName + ", and it should be visible via "
+        + "con.getClientInfo", appName, _conn.getClientInfo("ApplicationName"));
+    assertEquals("application_name was set to " + appName + ", and it should be visible via "
+        + "con.getClientInfo", appName, _conn.getClientInfo().get("ApplicationName"));
+  }
+
   public void testSetAppNameProps() throws SQLException {
     if (!TestUtil.haveMinimumServerVersion(_conn, "9.0")) {
       return;